Liquid crystal display device and method of fabricating the same

ABSTRACT

A liquid crystal display device including a pair of substrates, defined as a first substrate and a second substrate and a liquid crystal layer sandwiched between the pair of substrates. The device also includes a pixel electrode and an additional electrode formed on the first substrate, and a contact hole that is configured and arranged to connect the pixel electrode and the additional electrode. In certain embodiments, the contact hole is formed at a liquid crystal domain boundary. In other embodiments, an additional contact hole is also provided between the pixel electrode and a second additional electrode, and in such embodiments the contact hole and the additional contact hole are formed within different liquid crystal domains. Further, in certain embodiments, the pixel electrode includes a plurality of pixel electrode slits arranged in a pattern to form a plurality of liquid crystal domains within each pixel.

CROSS REFERENCE OF RELATED APPLICATION

This is a divisional of application Ser. No. 12/946,584, filed Nov. 15,2010, which is a continuation of application Ser. No. 12/191,017, filedAug. 13, 2008, now U.S. Pat. No. 7,956,969, issued Jun. 7, 2011, whichis a divisional of application Ser. No. 10/893,790, filed Jul. 16, 2004,now U.S. Pat. No. 7,450,206, issued Nov. 11, 2008, which is a divisionalof application Ser. No. 10/263,257, filed Oct. 2, 2002, now U.S. Pat.No. 6,778,229, issued Aug. 17, 2004, which is a CIP of application Ser.No. 10/107,989, filed Mar. 27, 2002, which is now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device to beused for television and other display apparatuses, to a method offabricating the same and, more particularly, to a liquid crystal displaydevice that uses a liquid crystal material containing a photosensitivematerial and a method of fabricating the same.

2. Description of the Related Art

A liquid crystal display device is a display device that comprises aliquid crystal sealed between two opposing substrates and that useselectrical stimulus for optical switching by exploiting theelectro-optical anisotropy of a liquid crystal. Utilizing the refractiveindex anisotropy that the liquid crystal possesses, the brightness ofthe light transmitted by the liquid crystal panel is controlled byapplying a voltage to the liquid crystal and thereby reorienting theaxis of the refractive index anisotropy.

In such a liquid crystal display device, it is extremely important tocontrol the alignment of liquid crystal molecules when no voltage isapplied to the liquid crystal. If the initial alignment is not stable,when a voltage is applied to the liquid crystal, the liquid crystalmolecules do not align in a predictable manner, resulting in aninability to control the refractive index. Various techniques have beendeveloped to control the alignment of liquid crystal molecules,representative examples including a technique that controls theinitially formed angle (pretilt angle) between the alignment film andthe liquid crystal and a technique that controls the horizontal electricfield formed between the bus line and the pixel electrode.

The same can be said of a display device that uses a liquid crystalmaterial containing a photosensitive material; specifically, in a liquidcrystal display mode in which the initial alignment is controlled byradiation of light in the presence of an applied voltage, the voltageapplication method during the radiation becomes important. The reason isthat, if the magnitude of the applied voltage differs, a change willoccur in the initially formed pretilt angle, resulting in a change intransmittance characteristics.

In connection with a first aspect of the invention, techniques calledpassive matrix driving and active matrix driving have usually been usedto drive liquid crystals; nowadays, with an increasing demand for higherresolution, the active matrix display mode that uses thin-filmtransistors (TFTs) is the dominant liquid crystal display mode. In aliquid crystal display having such TFTs, when radiating light onto theliquid crystal while applying a voltage to it, it is usually practicedto expose the liquid crystal to light radiation while applying a TFT ONvoltage to each gate bus line and a desired voltage to each data busline, as shown in FIGS. 1 and 2.

However, when such a liquid crystal exposure method is employed, ifthere is a line defect due to a bus line break or short, as shown inFIG. 3, the liquid crystal will be exposed to light when the liquidcrystal in the affected area cannot be driven, and a pretilt angledifferent from that in other areas will be formed in this defect area,resulting in the problem that the brightness in this area differs fromthe brightness in other areas.

Or, in the TFT channel ON state, a shift in the TFT threshold value canoccur due to exposure to ultraviolet radiation, as shown in FIG. 4,resulting in the problem that the region where the TFTs can be drivenstably shifts from the desired region.

On the other hand, in connection with a second aspect of the invention,displays using the TN mode have been the predominant type of activematrix liquid crystal display, but this type of display has had theshortcoming that the viewing angle is narrow. Nowadays, a techniquecalled the MVA mode or a technique called the IPS mode is employed toachieve a wide viewing angle liquid crystal panel.

In the IPS mode, liquid crystal molecules are switched in the horizontalplane by using comb-shaped electrodes, but a strong backlight isrequired because the comb-shaped electrodes significantly reduce thenumerical aperture. In the MVA mode, liquid crystal molecules arealigned vertically to the substrates, and the alignment of the liquidcrystal molecules is controlled by the use of protrusions or slitsformed in a transparent electrode (for example, an ITO electrode). Thedecrease in the effective numerical aperture due to the protrusions orslits used in MVA is not so large as that caused by the comb-electrodesin IPS, but compared with TN mode displays, the light transmittance ofthe liquid crystal panel is low, and it has not been possible to employMVA for notebook computers that require low power consumption.

When fine slits are formed in the ITO electrode, the liquid crystalmolecules tilt parallel to the fine slits, but in two differentdirections. If the fine slits are sufficiently long, liquid crystalmolecules located farther from a structure such as a bank that definesthe direction in which the liquid crystal molecules tilt are caused totilt randomly in two directions upon application of a voltage. However,the liquid crystal molecules located at the boundary between the liquidcrystal molecules caused to tilt in different directions, cannot tilt ineither direction, resulting in the formation of a dark area such as thatshown in FIG. 29. Further, in a structure where the liquid crystalmolecules are caused to tilt in two different directions in order toimprove viewing angle, if there are liquid crystal molecules that arecaused to tilt in the opposite direction, as shown in FIG. 29, theviewing angle characteristics degrade.

In connection with a third aspect of the invention, in an LCD (MVA-LCD)in which an N-type liquid crystal is aligned vertically and in which,upon application of a voltage, the molecules of the liquid crystal arecaused to tilt in a number of predefined directions by using alignmentprotrusions or electrode slits, the liquid crystal molecules are almostcompletely vertically aligned in the absence of an applied voltage, butare caused to tilt in the various predefined directions when a voltageis applied. The tilt directions of the liquid crystal molecules arecontrolled so that they always make an angle of 45° to the polarizerabsorption axis, but the liquid crystal molecules as a continuum cantilt in a direction intermediate between them. Furthermore, areas wherethe tilt direction of the liquid crystal molecules is displaced from thepredefined direction inevitably exist because of the effects of thehorizontal electric field, etc. at the time of driving or irregularitiesin the structure. In normally black displays where the polarizers arearranged in a crossed Nicol configuration, this means that dark areasappear when the display is driven in the white display state, and thescreen brightness thus decreases. To address this problem, in a liquidcrystal display device constructed by sandwiching between two substratesa liquid crystal composition containing a photopolymerizable orthermally polymerizable component, there is employed a technique thatpolymerizes the polymerizable component while applying a voltage,thereby defining the direction in which the liquid crystal moleculestilt in the presence of an applied voltage.

With this technique, however, if the polymerization is insufficient,image sticking can occur. This is believed to occur because the rigidityof the polymerized polymer is insufficient and deformation occurs due tothe realignment of the liquid crystal molecules at the time of voltageapplication. On the other hand, to sufficiently polymerize the polymer,the duration of light radiation must be increased, but in that case,take time at the time of volume production becomes a problem.

In connection with a fourth aspect of the invention, conventional liquidcrystal display devices predominantly use the TN mode in whichhorizontally aligned liquid crystal molecules are twisted between thetop and bottom substrates, but gray-scale inversion occurs in the midgray-scale range because the tilt angle of the liquid crystal differsdepending on the viewing direction, that is, the viewing angle. Toaddress this, a technique called the MVA mode has been proposed in whichvertically aligned liquid crystal molecules are tilted symmetrically inopposite directions to compensate for the viewing angle. In thistechnique, alignment control members made of an insulating material areformed on electrodes to control the liquid crystal tilt directions.However, since the liquid crystal molecules tilt in 180° oppositedirections on both sides of each alignment control member, a dark lineis formed and transmittance decreases. To obtain sufficienttransmittance, it is preferable to reduce the area occupied by thealignment control members by forming them spaced farther apart, but thiswould in turn slow the propagation speed of the tilt, resulting in aslow response speed.

To address this, a technique has been proposed in which a liquid crystalcomposition containing a polymerizable component is sandwiched betweensubstrates and, while applying a voltage, the polymerizable component ispolymerized, thereby defining the tilt direction of the liquid crystalmolecules. This achieves a faster response speed while retaining thetransmittance.

However, in the case of a liquid crystal display device in which thetilt direction of the liquid crystal molecules is defined bypolymerizing the polymerizable component in the liquid crystal whileapplying a voltage, there arises the problem that display unevennessoccurs after the polymerization of the polymerizable component, becauseof the separation of the liquid crystal and the polymerizable componentwhich occurs when the liquid crystal material is injected at high speedat the initial stage of injection or when there is an abrupt change inspeed near a frame edge.

In connection with a fifth aspect of the invention, in a liquid crystaldisplay device, it has traditionally been practiced to control thealignment direction of the vertically aligned panel by a TFT substratehaving slits in pixel electrodes and a color filter substrate havinginsulating protrusions, and it has therefore been necessary to form thedielectric protrusions on one of the substrates. Fabrication of such aliquid crystal display device therefore has involved the problem thatthe number of processing steps increases.

Furthermore, forming the protrusions within display pixels leads to theproblem that the numerical aperture decreases, reducing thetransmittance. In view of this, it has been proposed to control thealignment of the liquid crystal molecules by a polymerizable componentadded in the liquid crystal, in order to achieve multi-domains withoutusing dielectric layer protrusions. That is, the liquid crystal to whichthe polymerizable component is added is injected into the panel and,while applying a voltage, the polymerizable component is polymerized,thereby controlling the alignment of the liquid crystal molecules.

However, if the polymer composition that defines the alignment directiondoes not have a sufficient cross-linked structure, the polymer becomesflexible, and its restoring force weakens. If the polymer has suchproperties, then, when a voltage is applied to the liquid crystal tocause the liquid crystal molecules to tilt, and the liquid crystal isstill held in that state, the pretilt angle of the liquid crystal doesnot return to its initial state even after the applied voltage isremoved. This means that the voltage-transmittance characteristic haschanged, and this defect manifests itself as a pattern image sticking.

In connection with a sixth aspect of the invention, in an MVA-LCD inwhich liquid crystals having a negative dielectric anisotropy arevertically aligned, and in which the alignment of the liquid crystal inthe presence of an applied voltage is controlled in a number ofpredefined directions, without using a rubbing treatment but byutilizing the banks or slits formed on the substrates, the LCD providesexcellent viewing angle characteristics compared with conventional TNmode LCDs, but there is a disadvantage that white brightness is low andthe display is therefore relatively dark. The major reason is thatportions above the banks or slits correspond to the boundaries acrosswhich the liquid crystal alignment changes, and these portions appearoptically dark, reducing the transmittance of white. To improve this,the spacing between the banks or slits should be made sufficiently wide,but in that case, as the number of banks or slits for controlling theliquid crystal alignment decreases, it takes time until the alignmentstabilizes, thus slowing the response speed.

To obtain a brighter, faster response MVA panel by alleviating the abovedeficiency, it is effective to use a technique in which a liquid crystalcomposition containing a polymerizable component is sandwiched betweensubstrates and, while applying a voltage, the polymerizable component ispolymerized, thereby defining the tilt direction of the liquid crystalmolecules. For the polymerizable component, a monomer material thatpolymerizes by ultraviolet radiation or heat is usually used. It has,however, been found that this method has a number of problems associatedwith display unevenness.

That is, as this method is a rubbing-less method, if there occurs even aslight change in the structure or in electric lines of force, the liquidcrystal molecules may not align in the desired direction. As a result,there are cases where a contact hole or the like formed outside thedisplay area disrupts the alignment of the liquid crystal molecules andthe disruption affects the alignment of the liquid crystal moleculeswithin the display area, resulting in the formation of an abnormaldomain and causing the alignment to be held in that state. Furthermore,if structures that cause such disruptions in liquid crystal molecularalignment are located in the same alignment sub-region, abnormal domainsformed from the respective structures are concatenated, forming a largerabnormal domain. This causes the liquid crystal molecules outside andinside the display area to be aligned in directions other than thedesired directions, and the polymerizable component is polymerized inthat state, resulting in such problems as reduced brightness, slowerresponse speed, and display unevenness. FIG. 44 is a plan view showing apixel of a comparative example. In the pixel shown here, contact holesthat cause variations in cell thickness are not located at liquidcrystal domain boundaries, and two contact holes are located within thesame alignment sub-region. As a result, an abnormal domain is formed insuch a manner as to connect the two contact holes and, with thealignment held in this state, the polymerizable component ispolymerized, resulting in display performance degradations such asreduced brightness, slower response speed, and display unevenness.

Further, when a metal electrode such as a source electrode or a Csintermediate electrode is extended into the display pixel, there occursthe problem of reduced numerical aperture, and hence, reducedbrightness. Moreover, if an electrode with the same potential as thepixel electrode is extended into the display pixel, this also causesreduced brightness, slower response speed, and display unevenness.

In connection with a seventh aspect of the invention, while conductingstudies on the technique in which a liquid crystal compositioncontaining a polymerizable component is sandwiched between substratesand, while applying a voltage, the polymerizable component ispolymerized, thereby defining the tilt direction of the liquid crystalmolecules, the inventor et al. encountered the problem that when thesame pattern was displayed for a certain length of time, image stickingoccurred in the portion where the pattern was displayed. This isbelieved to occur because the polymerization is insufficient and thepolymer deforms. On the other hand, to sufficiently polymerize thepolymer, the duration of light radiation or heating must be increased,but in that case, tact time at the time of volume production becomes aproblem.

BRIEF SUMMARY OF THE INVENTION

The present invention aims to solve the above-enumerated problems of theprior art and to provide a method of fabricating a liquid crystaldisplay device which, during fabrication of the liquid crystal displaydevice, controls the alignment of liquid crystal molecules whenradiating light onto a liquid crystal composition containing aphotosensitive material, and thereby achieves substantially uniformalignment of the liquid crystal molecules and ensures stable operation.The invention also aims to provide such a liquid crystal display device.

To solve the above-enumerated problems, the first aspect of theinvention provides methods based on the following three major concepts.

1. Avoid the effects of wiring defects by driving the liquid crystal byapplying an AC voltage and using an electrical capacitance.

2. Avoid the effects of wiring defects by holding the wiring lines andelectrodes on the second substrate at the same potential.

3. Avoid the effects of wiring defects while screening TFT channelportions from light.

More specifically, based on the first concept, the first aspect of theinvention provides

(1) a method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance to the pixel electrode;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween; and

radiating light to the liquid crystal layer while applying an AC voltagebetween the common electrode and the pixel electrode by applying ACvoltages to the common electrode and the Cs bus line.

Based on the second concept, the invention provides

(2) a method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance to the pixel electrode;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween;

insulating the common electrode from the three bus lines, or connectingthe common electrode to the three bus lines via high resistance; and

radiating light to the liquid crystal layer while applying a DC voltagebetween the common electrode and the pixel electrode by applying a DCvoltage between the common electrode and the three bus lines (the gatebus line, the data bus line, and the Cs bus line) formed on the secondsubstrate, or

(3) a method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, a Cs bus line that forms an electrical capacitanceto the pixel electrode, and a repair line intersecting with at least oneof the data bus and gate bus lines;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween; and

radiating light to the liquid crystal layer while applying a DC voltagebetween the common electrode and the pixel electrode by applying a DCvoltage between the common electrode and the four bus lines (the gatebus line, the data bus line, the Cs bus line, and the repair line)formed on the second substrate, or

(4) a method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance to the pixel electrode;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween; and

connecting the common electrode, via high resistances, to the three buslines (the gate bus line, the data bus line, and the Cs bus line,)formed on the second substrate, and radiating light to the liquidcrystal layer while applying a DC voltage between the common electrodeand the pixel electrode by applying a DC voltage between the commonelectrode and at least one of the bus lines.

Based on the third concept, the invention provides

(5) a method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance to the pixel electrode;

forming a CF resin or a light blocking pattern on a channel portion ofthe thin-film transistor;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween;

electrically connecting adjacent data bus lines at both ends thereof;and

radiating light to the liquid crystal layer while applying an AC voltagebetween the common electrode and the pixel electrode by applying atransistor ON voltage to the gate bus line and an AC voltage between thecommon electrode and the data bus line, or

(6) a method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, a Cs bus line that forms an electrical capacitanceto the pixel electrode, and a repair line intersecting with the data busline;

forming a CF resin or a light blocking pattern on a channel portion ofthe thin-film transistor;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween;

connecting at least one data bus line with at least one repair line bylaser radiation or another method; and

radiating light to the liquid crystal layer while applying an AC voltagebetween the common electrode and the pixel electrode by applying atransistor ON voltage to the gate bus line and an AC voltage between thecommon electrode and the data bus line and repair line (the repair lineis at the same potential as the data bus line).

In the second aspect of the invention, there is provided

(7) a method of fabricating a vertical alignment liquid crystal displaydevice, comprising:

forming a liquid crystal layer by filling a liquid crystal compositioninto a gap between two substrates each having a transparent electrodeand an alignment control film for causing liquid crystal molecules toalign vertically, the liquid crystal composition having a negativedielectric anisotropy and containing a polymerizable monomer; and

polymerizing the monomer while applying a voltage between opposingtransparent electrodes, and thereby providing a pretilt angle to theliquid crystal molecules, and wherein:

before polymerizing the monomer, a constant voltage not smaller than athreshold voltage but not greater than a saturation voltage is appliedbetween the opposing transparent electrodes for a predetermined periodof time, and thereafter, the voltage is changed to a prescribed voltageand, while maintaining the prescribed voltage, ultraviolet radiation orheat is applied to the liquid crystal composition to polymerize themonomer.

That is, when polymerizing the polymerizable monomer, a voltage slightlyhigher than the threshold voltage is applied and, after the liquidcrystal molecules are tilted in the right direction, the voltage israised to a higher level; then, while maintaining the voltage at thehigher level, the polymerizable monomer is polymerized.

In the third aspect of the invention, there is provided

(8) a method of fabricating a liquid crystal display device, comprising:

forming a liquid crystal layer by filling a liquid crystal compositioncontaining a polymerizable monomer into a gap between two substrateseach having a transparent electrode; and

polymerizing the monomer while applying a voltage between opposingtransparent electrodes, and thereby providing a pretilt angle to liquidcrystal molecules while, at the same time, controlling the direction inwhich the liquid crystal molecules tilt in the presence of an appliedvoltage, and wherein:

light radiation for polymerizing the polymerizable monomer is performedin at least two steps.

In the fourth aspect of the invention, there is provided

(9) a liquid crystal display device in which a liquid crystalcomposition containing a photopolymerizable or thermally polymerizablecomponent is sandwiched between substrates and the polymerizablecomponent is photopolymerized or thermally polymerized while applying avoltage, thereby defining the direction in which liquid crystalmolecules tilt in the presence of an applied voltage, wherein aplurality of injection ports for injecting therethrough the liquidcrystal composition containing the polymerizable component are formed inone side of the liquid crystal display device, and spacing between therespective injection ports is not larger than one-fifth of the length ofthe side in which the injection ports are formed, or

(10) a liquid crystal display device in which a liquid crystalcomposition containing a photopolymerizable or thermally polymerizablecomponent is sandwiched between substrates and the polymerizablecomponent is polymerized while applying a voltage, thereby defining thedirection in which liquid crystal molecules tilt in the presence of anapplied voltage, wherein a cell gap in a frame edge BM area is notlarger than the cell gap of a display area, or

(11) a liquid crystal display device in which a liquid crystalcomposition containing a photopolymerizable or thermally polymerizablecomponent is sandwiched between substrates and the polymerizablecomponent is polymerized while applying a voltage, thereby defining thedirection in which liquid crystal molecules tilt in the presence of anapplied voltage, wherein a main seal or an auxiliary seal is formed in aframe edge BM area to eliminate a cell gap in the frame edge BM area, or

(12) a liquid crystal display device in which a liquid crystalcomposition containing a photopolymerizable or thermally polymerizablecomponent is sandwiched between substrates and the polymerizablecomponent is polymerized while applying a voltage, thereby defining thedirection in which liquid crystal molecules tilt in the presence of anapplied voltage, wherein an auxiliary seal is formed so that a materialwhose concentration of the polymerizable material relative to liquidcrystal is abnormal is guided into a BM area.

In the fifth aspect of the invention, there is provided

(13) a method of fabricating a liquid crystal display device,comprising:

forming a common electrode and a color filter layer on a firstsubstrate;

constructing a second substrate from an array substrate on which areformed a gate bus line layer, a gate insulating film layer, a drain busline layer, a protective film layer, and a pixel electrode layer;

forming fine slits in the pixel electrode layer in such a direction thata pixel is divided by the slits into at least two sub-regions;

forming on each of the two substrates a vertical alignment film forvertically aligning liquid crystal molecules;

forming a liquid crystal layer by filling an n-type liquid crystalcomposition having a negative dielectric anisotropy into a gap betweenthe two substrates, the liquid crystal composition containing anultraviolet curable resin having a liquid crystal backbone;

radiating ultraviolet light while applying to the liquid crystalmolecules a voltage not smaller than a threshold value of the liquidcrystal molecules, thereby defining the direction in which the liquidcrystal molecules tilt in the presence of an applied voltage; and

arranging two polarizers on top and bottom surfaces of the liquidcrystal display device in a crossed Nicol configuration with theabsorption axes thereof oriented at an angle of 45 degrees to thealignment directions of the liquid crystal molecules.

In the sixth aspect of the invention, there is provided

(14) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein any portion where cellthickness varies by 10% or more due to design constraints is located ata liquid crystal domain boundary, or

(15) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a contact hole thatconnects between a source electrode and a pixel electrode is formed at aliquid crystal domain boundary, or

(16) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a contact hole thatconnects between a Cs intermediate electrode and a pixel electrode isformed at a liquid crystal domain boundary, or

(17) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, and liquid crystal alignment isdivided between two or more sub-regions, wherein more than one portionwhere cell thickness varies by 10% or more due to design constraintsdoes not exist, or

(18) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, and liquid crystal alignment isdivided between two or more sub-regions, wherein more than one contacthole is not formed in the same sub-region, or

(19) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a pixel electrode, asource electrode, and a Cs intermediate electrode are connected by asingle contact hole, or

(20) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a metal electrode iswired along a liquid crystal domain boundary within a display pixel, or

(21) a liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein an electrode having thesame potential as a pixel electrode is not wired in a slit portion ofthe pixel electrode within a display pixel.

In the seventh aspect of the invention, there is provided a

(22) a method of fabricating a liquid crystal display device,comprising: forming a liquid crystal layer by filling a liquid crystalcomposition containing a polymerizable monomer into a gap between a pairof substrates having electrodes; and polymerizing the monomer byradiating ultraviolet light to the liquid crystal composition whileapplying a prescribed liquid crystal driving voltage between opposingelectrodes, and wherein: after polymerizing the monomer, additionalultraviolet radiation is applied to the liquid crystal compositionwithout applying the liquid crystal driving voltage or while applying avoltage of a magnitude that does not substantially drive the liquidcrystal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing one example of a liquid crystaldisplay device fabricated according to the prior art.

FIG. 2 is a schematic cross-sectional view of the liquid crystal displaydevice of FIG. 1.

FIG. 3 is a schematic plan view showing one example of the liquidcrystal display device fabricated according to the prior art.

FIG. 4 is a graph showing one example of a TFT threshold value shift asobserved in the liquid crystal display device fabricated according tothe prior art.

FIG. 5 is a schematic plan view showing one example of electricalcoupling in a prior art TFT liquid crystal panel.

FIG. 6 is a schematic plan view showing another example of electricalcoupling in a prior art TFT liquid crystal panel.

FIG. 7 is a schematic plan view for explaining one example of afabrication method for a liquid crystal display device according to thepresent invention.

FIG. 8 is a schematic plan view for explaining one example of afabrication method for a liquid crystal display device according to thepresent invention.

FIG. 9 is a schematic plan view showing a liquid crystal display deviceaccording to a first embodiment.

FIG. 10 is a graph showing the display characteristics of the liquidcrystal display device according to the first embodiment.

FIG. 11 is a graph showing the display characteristics of the liquidcrystal display device according to the first embodiment.

FIG. 12 is a schematic plan view showing a liquid crystal display deviceaccording to a second embodiment.

FIG. 13 is a diagram for explaining one method used in a thirdembodiment to short a Cs bus line to a common electrode.

FIG. 14 is a diagram for explaining another method used in the thirdembodiment to short the Cs bus line to the common electrode.

FIG. 15 is a schematic plan view showing a liquid crystal display deviceaccording to a fourth embodiment.

FIG. 16 is a graph showing results in a sixth embodiment.

FIG. 17 is a schematic plan view showing a liquid crystal display deviceaccording to a seventh embodiment.

FIG. 18 is a schematic plan view showing a liquid crystal display deviceaccording to an eighth embodiment.

FIG. 19 is a schematic plan view showing a liquid crystal display deviceaccording to a ninth embodiment.

FIG. 20 is a schematic plan view showing another example of the liquidcrystal display device according to the ninth embodiment.

FIG. 21 is a schematic plan view showing another example of the liquidcrystal display device according to the ninth embodiment.

FIG. 22 is a schematic plan view showing a liquid crystal display deviceaccording to a 10th embodiment.

FIG. 23 is a schematic cross-sectional view showing a liquid crystaldisplay device according to an 11th embodiment.

FIG. 24 is a schematic plan view showing a liquid crystal display deviceaccording to a 12th embodiment.

FIG. 25 is a schematic plan view of a liquid crystal panel fabricatedaccording to a 13th embodiment.

FIG. 26 is a schematic cross-sectional view showing one example of theliquid crystal panel of FIG. 25.

FIG. 27 is a schematic cross-sectional view showing another example ofthe liquid crystal panel of FIG. 25.

FIG. 28 is a schematic plan view of a liquid crystal panel fabricatedaccording to a 14th embodiment.

FIG. 29 is a schematic plan view for explaining a prior art example.

FIG. 30 is a schematic plan view for explaining a prior art example.

FIG. 31 is a schematic cross-sectional view showing the liquid crystalpanel of FIG. 30.

FIG. 32 is a schematic diagram for explaining a prior art example.

FIG. 33 is a schematic diagram showing UV radiation methods used infirst and second comparative examples and 15th to 17th embodiments.

FIG. 34 is a schematic plan view showing a liquid crystal panelaccording to an 18th embodiment.

FIG. 35 is a schematic cross-sectional view showing a liquid crystalpanel according to a 19th embodiment.

FIG. 36 is a schematic cross-sectional view showing a liquid crystalpanel according to a 20th embodiment.

FIG. 37 is a schematic plan view showing a liquid crystal panelaccording to a 21st embodiment.

FIG. 38 is a schematic cross-sectional view showing a liquid crystalpanel according to a 22nd embodiment.

FIG. 39 is a schematic plan view of the liquid crystal panel accordingto the 22nd embodiment.

FIG. 40 is a schematic diagram for explaining how the alignments ofliquid crystal molecules are controlled in the 22nd embodiment.

FIG. 41 is a process flow diagram of the 22nd embodiment.

FIG. 42 is a schematic diagram showing equipment used in a 23rdembodiment.

FIG. 43 is a schematic cross-sectional view showing a liquid crystalpanel according to a 24th embodiment.

FIG. 44 is a plan view showing a comparative example of a pixel in aliquid crystal display device.

FIG. 45 is a diagram showing a plan view and a cross-sectional view of apixel in a liquid crystal display device according to a 25th embodiment.

FIG. 46 is a diagram showing a plan view of a pixel in a liquid crystaldisplay device according to a 26th Embodiment.

FIG. 47 is a diagram showing a plan view of a pixel in a liquid crystaldisplay device according to a 27th Embodiment.

FIG. 48 is a diagram showing a plan view and a cross-sectional view of apixel in a liquid crystal display device according to a 28th embodiment.

FIG. 49 is a schematic diagram showing a plan view and a side viewillustrating a method of additional ultraviolet radiation according to a29th embodiment.

FIG. 50 is a graph showing the relationship between the amount ofadditional ultraviolet radiation and the image sticking ratio accordingto the 29th embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The first aspect of the invention discloses the following methods asspecific implementations thereof.

1) The method described in above item (1), wherein the common electrodeand the Cs bus line are insulated from each other or connected via highresistance when radiating the light to the liquid crystal layer.

2) The method described in above item (1), wherein after radiating thelight to the liquid crystal layer, the common electrode and the Cs busline are electrically connected together.

3) The method described in above item (1), wherein a transistor OFFvoltage is applied to the gate bus line.

4) The method described in above item (1), wherein initially the liquidcrystal layer is vertically aligned and, by radiating the light whileapplying a voltage to the liquid crystal composition containing thephotosensitive material, the average angle of the liquid crystal to analignment film is set smaller than a polar angle of 90°.

5) The method described in above item (1), wherein the AC frequency,when applying the AC voltage, is set within a range of 1 to 1000 Hz.

6) The method described in above item (2), wherein adjacent gate buslines or data bus lines are electrically connected together at both endsthereof.

7) The method described in above item (2), wherein after radiating thelight to the liquid crystal layer, the common electrode and the Cs busline are electrically connected together.

8) The method described in above item (2), wherein initially the liquidcrystal layer is vertically aligned and, by radiating light whileapplying a voltage to the liquid crystal composition containing thephotosensitive material, the average angle of the liquid crystal to thealignment film is set smaller than a polar angle of 90°.

Usually, a TFT liquid crystal panel has electrical couplings such asshown in FIG. 5. At this time, the two electrodes, that is, the commonelectrode and the pixel electrode, form an electrical capacitance C1c byholding therebetween such materials as the liquid crystal and alignmentfilm. The Cs bus line in the figure forms an electrical capacitance Csbetween it and each pixel electrode, and controls the amount of voltagefluctuation and the amount of charge to be written to the pixelelectrode.

Usually, the writing of a charge to the pixel electrode is done via athin-film transistor (TFT), and to achieve this, the gate bus line thatacts as a switch for writing and the data bus line used to write avoltage to the pixel electrode are arranged in a matrix form in such amanner as to sandwich the pixel electrode between them.

Fatal pattern defects (wiring defects) that can occur in the TFT liquidcrystal panel include:

a. Gate bus line breakage

b. Data bus line breakage

c. Cs bus line breakage

d. Intra-layer short between gate bus line and Cs bus line

e. Interlayer short between gate bus line and data bus line

f. Interlayer short between Cs bus line and data bus line

These defects decrease fabrication yields. To counter these defects,redundant design techniques are employed, and repairs are frequentlydone not only immediately after the formation of the pattern but alsoafter the cell is completed by injecting the liquid crystal. Since thedefects a, c, and d are defects introduced in the first layer formed onthe substrate, rework is easy, and usually they are not defects thatrequire reworking after the cell has been completed. In particular, forthe defect c, since the Cs bus line is a common electrode, it is easy toform a redundant pattern, for example, by bundling the lines at bothends of the LCD panel, as shown in FIG. 6, and if the electricalconductivity of the film is higher than a certain value, this defect canbe avoided. On the other hand, the defects b, e, and f are defects thatoften require reworking after the cell has been completed and, whenradiating light to the liquid crystal, the liquid crystal cannot bedriven normally by applying a write voltage via the data bus line.

In view of this, in the method of the invention based on the firstconcept, writing is performed by applying a voltage between the twocommon electrodes, rather than applying a write voltage to the liquidcrystal via the data bus line. The above-described problem that ariseswhen writing via the data bus line can then be ignored to some degree.

The reason is that, as the pixel electrode is treated as a floatinglayer, it is unaffected by such defects as b and e. This is because theapplication of an AC voltage between the common electrode and the Cs busline results in the formation of a circuit that applies an AC voltageacross a series coupling where pixel potential is approximately C1s andCs, the applied voltage to the liquid crystal part being given byApplied voltage to liquid crystal part=Z1c/(Z1c+Zc)×AC voltagewhere Z1c and Zc are the respective impedances.

At this time, if the gate bus line voltage is floating, the TFT issubstantially OFF, and avoidance of the threshold value shift, anotherobject of the invention, is automatically achieved. In practice, it isalso possible to actively apply an OFF voltage to the gate bus line; inthis case, the electrical capacitance Cgc that the gate bus line and thecommon electrode form and the capacitance Cgs that the gate bus line andthe pixel electrode form affect the value of the applied voltage to theliquid crystal part.

The method of the invention based on the second concept proposes toavoid the defects b, e, and f by applying a DC voltage and holding thewiring lines and electrodes on the second substrate at the samepotential as specified in the present invention.

For the defects e and f, in theory, a condition in which the short iscompletely invisible can be achieved if voltages on the data bus line,the Cs bus line, and the gate bus line are all the same. Of course, thisis intended to be achieved only during exposure to light. For example,when a DC voltage of 0 V is applied to the common electrode and a DCvoltage of 5 V to the data bus line, the Cs bus line, and the gate busline, it follows that 5 V is applied to the pixel electrode. That is,though the data bus line and the pixel electrode are connected via theTFT, the charge gradually flows into the pixel electrode which is thuscharged up to 5 V after a sufficient time. This means that the conditionof common electrode (0 v)—pixel electrode (5 V) is achieved, and thevoltage can thus be applied to the liquid crystal. Since liquid crystalsused for TFT displays usually have high resistance, movement of ions inthe liquid crystal layer can virtually be neglected.

According to the above concept, means for avoiding the defect b can alsobe obtained. That is, usually an ESD circuit (Electrostatic Dischargecircuit) is formed in a TFT panel for protection against electrostaticdischarge, as shown in FIG. 6. This is equivalent to achieving acondition in which the respective bus lines are connected via highresistance. As in the case of FIG. 6, even when there is a break in adata bus line, if there is any voltage input path on the opposite side,the desire voltage for application can be obtained after a sufficienttime even if the connection is made by high resistance.

The method of the invention based on the third concept is aimed atradiating light to the liquid crystal by avoiding a wiring defect whiledirectly preventing UV radiation to TFT channel portions. In this case,normal driving is possible when applying a voltage to the liquidcrystal. This method, however, proposes to apply a voltage to the busline from both ends thereof in order to avoid the effects of a linedefect. This makes it possible to avoid the effects of the defect b.

With advances in inspection techniques in recent years, it has becomepossible to detect defect coordinates with high accuracy before the cellis completed. If only defect coordinates can be confirmed, then a defectof type e or f can be converted to a defect of type b by the processingsuch as shown in FIG. 7. If this repair can be done before radiatinglight onto the liquid crystal, the effects of a line defect can beavoided by combining this technique with the method proposed here.

The method of the invention can also be applied to the following cases.

First, the method can be applied to the TFT design called the Cs-on-gatetype, as shown in FIG. 8. Though the structure shown does not have Csbus lines, the method of the invention based on the second or thirdconcept can likewise be applied to this type of design. In the case ofthe method of the invention based on the first concept, when thecapacitances formed by the pixel electrode and the respective gate buslines are denoted by Cgs1 and Cgs2, it is expected that the appliedvoltage to the liquid crystal part is substantially determined byApplied voltage to the liquid crystal part=Z1c/(Z1c+Zgs)×AC voltagewhere Zgs is the impedance.

Second, the method can be applied to the fabrication process of a liquidcrystal display device in which a uniform DC voltage is applied to theliquid crystal during the fabrication thereof. For example, whendetermining the initial alignment of a ferroelectric liquid crystal,there are cases where it is required to apply a DC voltage uniformlyover the entire surface; in such cases also, line defects may become aproblem as in the case of the method of the present invention.

Third, the method can be applied to the case where the IPS mode iscombined with a photosensitive material. In the case of IPS, thedirection of the electric field formed at the time of exposure isassumed not only between the top and bottom substrates but also betweenthe comb-shaped electrodes. Though the method of the invention assumesthat the common electrode is formed on the first substrate, the methodcan also be applied to the case where a voltage is applied between thepixel electrode and the common electrode on the second substrate.

In the liquid crystal display device fabricated according to the methodof the present invention, generally, the spacing between the first andsecond substrates is maintained constant by means of a structuresupporting them or by means of gap support members such as plastic beadsas shown in FIG. 2, and the liquid crystal material held between the twosubstrates is sealed into the gap between them by fixing its peripherywith an adhesive layer.

The second aspect of the invention discloses the following methods asspecific implementations thereof.

1) The method described in above item (7) wherein, after a constantvoltage not smaller than the threshold voltage but not greater than thethreshold voltage+1 V is applied between the opposing transparentelectrodes for a time not shorter than 10 seconds, the voltage ischanged by applying a voltage not smaller than a voltage to be appliedto produce a white display state and, while maintaining the voltage, theultraviolet radiation or heat is applied to the liquid crystalcomposition to polymerize the monomer.

2) The method described in above item (7), wherein the transparentelectrode on at least one of the substrates has a 0.5- to 5-micron fineslit structure.

3) The method described in above item (7), wherein the fine slitstructure is formed from fine ITO slits formed in vertical direction.

4) The method described in above item (7), wherein the length of each ofthe fine ITO slits is approximately one half the vertical length of thepixel electrode.

5) The method described in above item (7), wherein the fine slitstructure is formed from fine ITO slits formed in horizontal direction.

6) The method described in above item (7), wherein the length of each ofthe fine ITO slits is approximately equal to the horizontal length ofthe pixel electrode.

7) The method described in above item (7), wherein at least one of thesubstrates has 0.1- to 5-micron high protrusions protruding into the gapbetween the substrates.

In today's MVA, light transmittance is low because banks or ITO slitsare arranged in complicated manner so that, to achieve a wider viewingangle, the liquid crystal molecules tilt in four different directionswhen a voltage is applied. To simplify this structure, a structure suchas shown in FIGS. 30 and 31, in which the liquid crystal molecules tiltin two different directions when a voltage is applied, has beenconsidered. In MVA, the direction in which the liquid crystal moleculestilt is sequentially defined by the electric field formed on the banksor ITO slits in the order of increasing distance from the banks orslits. If the spacing between the banks or ITO slits is very wide asshown in FIGS. 30 and 31, it takes time to propagate the molecular tiltthroughout the liquid crystal, and this greatly slows the panel responsewhen a voltage is applied.

In view of this, a technique has been employed in which a liquid crystalcomposition containing a polymerizable monomer is injected and, whileapplying a voltage, the monomer is polymerized, thereby fixing thedirection in which the liquid crystal molecules tilt.

Another problem has been that since liquid crystal molecules are causedto tilt in a direction rotated 90° from the intended direction due tothe electric field formed at a pixel electrode edge near the data busline, a relatively large dark area is formed in the pixel, asillustrated in FIG. 32 which shows the pixel observed under amicroscope. In view of this, fine slits are formed in the ITO pixelelectrode on the TFT side substrate to control the molecular alignmentby means of electric fields. When fine slits are formed in the ITO pixelelectrode, the liquid crystal molecules tilt in parallel to the fineslits. Furthermore, since the alignment direction of all the liquidcrystal molecules is determined by the electric fields, the effects ofthe electric field formed at the pixel edge can be minimized.

When a high voltage is applied abruptly, the liquid crystal moleculesare caused to tilt wildly by electrostatic energy. Those liquid crystalmolecules that are tilted in the direction opposite to the direction inwhich they should have been tilted attempt to stand up and tilt in theright direction because the molecules in that state are unstable fromthe viewpoint of energy. It takes much elastic energy for them to standup and tilt in the right direction because, in the process, they mustovercome the electrostatic energy. If they cannot overcome theelectrostatic force, the liquid crystal molecules tilted in the oppositedirection will enter a metastable state and remain in that state.However, if a voltage slightly higher than the threshold is applied, theliquid crystal molecules tilted in the opposite direction can be causedto stand up and tilt in the right direction by overcoming theelectrostatic energy with small elastic energy. Once the liquid crystalmolecules are tilted in the right direction, they will not tilt in theopposite direction if the voltage is raised. Therefore, when the monomeris polymerized with the liquid crystal molecules tilted in the rightdirection, the state of alignment in the right direction is memorized,and when the voltage is applied next time, the liquid crystal moleculeswill not tilt in the opposite direction.

In view of this, after the alignment is set by applying a voltageslightly higher than the threshold voltage, if the voltage is raised toa prescribed level and, in this condition, the polymerizable monomer ispolymerized, good molecular alignment can be achieved.

As for the fine ITO slits, if the slit width is too small, the slits maybreak, and conversely, if the slit width is made too large, the liquidcrystal molecules may not tilt in the direction parallel to the slits.Further, if the fine ITO slits are made too close together, the risk ofshorts between them increases, and conversely, if the slits are spacedtoo far apart, the liquid crystal molecules may not tilt in thedirection parallel to the slits. It is therefore preferable that thefine slits and fine electrodes be each formed to have a width within arange of 0.5 microns to 5 microns.

The third aspect of the invention discloses the following methods asspecific implementations thereof.

1) The method described in above item (8), wherein at least one of theplurality of light radiation steps is performed while applying a voltageto the liquid crystal layer.

2) The method described in above item (8), wherein the plurality oflight radiation steps are performed without applying a voltage, eitherbefore or after or both before and after the light radiation that isperformed in the presence of an applied voltage.

3) The method described in above item (8), wherein the plurality oflight radiation steps are respectively performed with different lightintensities.

4) The method described in above item (8), wherein the light radiationthat is performed in the presence of an applied voltage is performedwith a light intensity of 50 mw/cm² or higher.

5) The method described in above item (8), wherein the light radiationthat is performed without applying a voltage is performed with a lightintensity of 50 mW/cm² or lower.

6) The method described in above item (8), wherein the liquid crystal isan N-type liquid crystal, and the liquid crystal molecules aresubstantially vertically aligned in the absence of an applied voltage.

7) The method described in above item (8), wherein the liquid crystaldisplay device is an active matrix LCD in which an array of TFTs asswitching devices is formed on one of the two substrates.

8) The method described in above item (8), wherein the polymerizablemonomer is a liquid crystalline or non-liquid-crystalline monomer, andis polymerized by ultraviolet radiation.

9) The method described in above item (8), wherein the polymerizablemonomer is bifunctional acrylate or a mixture of bifunctional acrylateand monofunctional acrylate.

To prevent polymer image sticking, it is preferable that there be noresidual monomers and all monomers be polymerized. It was experimentallyfound that if polymerization is performed with insufficient UV radiationor with strong UV radiation but for a short period, unreacted monomerswill remain due to insufficient radiation time, and therefore that it ispreferable to perform polymerization with low UV strength for asufficient period of time. However, if the amount of radiation isincreased enough that no unreacted monomers remain, then there arisesthe problem that the contrast decreases, but this problem occurs whenthe UV radiation is performed in the presence of an applied voltage. Inview of this, in the present invention, the UV radiation forpolymerization is performed in a plurality of steps. By performing theradiation steps, some in the presence of an applied voltage and othersin the absence of an applied voltage, the residual monomer problem canbe solved without excessively reducing the pretilt of liquid crystalmolecules. It is also preferable to vary the UV radiation strengthbetween the steps. For example, after performing the first radiationstep with low UV strength, the second radiation is performed with highUV strength in the presence of an applied voltage, which is followed bythe radiation performed with low UV strength. Since a plurality ofpanels can be processed together in the radiation step performed in theabsence of an applied voltage, the increase in the radiation time inthis step does not become a problem; this means that the radiation timein the step performed in the presence of an applied voltage, which isthe rate-determining step, can be reduced by increasing the UV radiationstrength.

In the method of the present invention, pretilt decreases during the UVradiation performed in the presence of an applied voltage, but no changeoccurs in the pretilt during the UV radiation performed in the absenceof an applied voltage. Accordingly, the UV radiation process is dividedinto a plurality of steps, and the time of UV radiation is reduced whenperforming it in the presence of an applied voltage and increased whenperforming it in the absence of an applied voltage; by so doing, thepretilt angle is prevented from becoming too large, and the monomers canbe completely polymerized, leaving no unreacted monomers. Alternatively,if preliminary radiation is performed to slightly promote the reactionof the monomers preparatory to the UV radiation performed in thepresence of an applied voltage, unreacted residual monomers can befurther reduced.

The effect of performing the UV radiation in intermittent fashion willbe described below. In the case of a TFT-LCD, if UV is radiated fromeither the TFT side or the CF side, there remain unradiated portionsbecause of the presence of light blocking portions. Unreacted monomersin these portions migrate into the display area as the time elapses, andeventually cause image sticking. However, when a time interval isprovided between the radiation steps as described above, unreactedmonomers are allowed to migrate into the display area during thatinterval, and are exposed to UV radiation, and eventually, almost allmonomers hidden behind the light blocking portions are reacted,achieving an LCD substantially free from image sticking.

Thus, according to the present invention, a polymer-fixed MVA-LCD havinghigh contrast and free from image sticking can be achieved, and besides,the time of the polymerization step can be reduced compared with theprior art.

The fourth aspect of the invention discloses the following devices asspecific implementations thereof.

1) The device described in above item (9), wherein the injection portsare spaced away from a display edge by a distance not greater thantwo-fifths of the length of the side in which the injection ports areformed.

2) The device described in above item (10), wherein the area where thecell gap is not larger than the cell gap of the display area is spacedaway from a cell forming seal by a distance not greater than 0.5 mm.

3) The device described in any one of the above items (9) to (12),wherein the liquid crystal composition contains a non-liquid-crystalcomponent or a component whose molecular weight and surface energy aredifferent from those of a liquid-crystal component.

In the device (9) of the present invention, to reduce display unevennesswhich could occur after polymerization of the polymerizable componentdue to separation of the liquid crystal and the polymerizable component,the liquid crystal composition must be thoroughly stirred at the initialstage of the injection process of the liquid crystal composition so thatabnormal concentration portions of the polymerizable component andliquid crystal will not be formed, and so that localized increases inspeed will not occur during the injection process. In the above device,this is achieved by optimizing the number of injection ports and thepositions of the injection ports.

In the devices (10) and (11) of the present invention, to reduce displayunevenness which could occur after polymerization of the polymerizablecomponent due to separation of the liquid crystal and the polymerizablecomponent, it becomes necessary, at the initial stage of the liquidcrystal injection process, to prevent abnormal concentration portions ofthe polymerizable component and liquid crystal from forming andmigrating from the frame edge into the display area resulting inagglomeration of the abnormal portions, and also to prevent theseparation of the liquid crystal and polymerizable component due toincreases in speed in the frame edge portion. In the above devices,therefore, to reduce the display unevenness, the cell thickness at theframe edge is made not greater than that of the display area, thedistance between the frame edge and the seal is made not greater than apredetermined value, and the frame edge portion is filled with theauxiliary seal.

In the device (12) of the present invention, any abnormal concentrationportion of the polymerizable component and liquid crystal is guidedoutside the display area before polymerizing the polymerizablecomponent, thereby preventing the occurrence of display unevenness.

According to the invention, in the liquid crystal display device inwhich the polymerizable component dispersed in the liquid crystal isphotopolymerized or thermally polymerized while applying a voltage,thereby defining the direction in which the liquid crystal moleculestilt in the presence of an applied voltage, display unevenness does notoccur near the side where the injection ports for the liquid crystalcomposition are formed. Accordingly, the liquid crystal display deviceof the invention can achieve high display quality.

The fifth aspect of the invention discloses the following methods asspecific implementations thereof.

1) The method described in above item (13), wherein the step ofradiating the ultraviolet light to the liquid crystal compositioninjected between the two substrates is divided in two or more steps andperformed by using ultraviolet light of different intensities.

2) The method described in above item (13), wherein the step ofradiating the ultraviolet light to the liquid crystal compositioninjected between the two substrates is divided in two steps consistingof the step of radiating the ultraviolet light while applying to theliquid crystal molecules a voltage not smaller than the threshold valueof the liquid crystal molecules and the step of radiating theultraviolet light without applying a voltage to the liquid crystalmolecules.

3) The method described in above item (13), wherein the step ofradiating the ultraviolet light to the liquid crystal compositioninjected between the two substrates is divided in two steps andperformed by applying respectively different voltages to the liquidcrystal molecules.

4) The method described in above item (13), wherein the step ofradiating the ultraviolet light for polymerizing the ultravioletpolymerizable resin contained in the liquid crystal composition injectedbetween the two substrates is divided in two or more steps and performedby using a plurality of ultraviolet radiation units of different lightintensities.

5) The method described in above item (13), wherein the ultravioletradiation to the liquid crystal composition injected between the twosubstrates is applied from the array substrate side.

6) The method described in above item (13), wherein the second substrateis constructed from an array substrate on which the color filter layeris formed, the common electrode being formed on the first substrate, andthe ultraviolet radiation to the liquid crystal composition injectedbetween the two substrates is applied from the first substrate side.

According to the present invention, the polymer material added tocontrol the tilt angle and azimuth angle of the liquid crystal moleculescan take a structure that suitably controls the tilt angle of the liquidcrystal molecules.

For example, if light is radiated sufficiently in the presence of anapplied voltage, a rigid cross-linked structure can be formed, butprocessing takes too much time, and the cost increases because thenumber of processing units must be increased for mass production orbecause the processing capacity decreases.

As described above, according to the present invention, a fast responseliquid crystal display device can be achieved that is free from imagesticking, has a wide viewing angle made possible by reliable four-domaintechnology, provides high contrast by vertical alignment, and has thealignment of the liquid crystal molecules controlled using a polymer.

The sixth aspect of the invention discloses the following devices asspecific implementations thereof.

1) The device described in any one of the above items (14) to (21),wherein the liquid crystal layer is sandwiched between a substrate inwhich a color filter layer of red, blue, and green is formed on a TFTsubstrate, and a substrate on which a common electrode is formed.

In the devices (14) to (16) of the present invention, to prevent theformation of an abnormal domain in the liquid crystal and to align theliquid crystal in the desired direction, it is essential that any areawhere the cell thickness varies, which could become the start point ofan abnormal domain, be located at a domain boundary when the liquidcrystal is aligned in the desired direction. This serves to alleviatethe problems of low brightness, slow response speed, and displayunevenness caused by the presence of an abnormal domain.

In the devices (17) and (18) of the present invention, if a liquidcrystal domain occurs, the area of that domain must be minimized. Toachieve this, provision must be made so that more than one structurethat could become the start point of an abnormal domain will not becontained in the same alignment sub-region. This serves to alleviate theproblems of low brightness, slow response speed, and display unevennesscaused by the presence of an abnormal domain.

In the device (19) of the present invention, the number of contact holesthat could become the start points of abnormal domains is reduced toone, thus making it possible to reduce the number of abnormal domainsand increase the numerical aperture.

In the device (20) of the present invention, to prevent the numericalaperture from decreasing due to the presence of the metal electrodewithin the display pixel, it is effective to wire the metal electrodealong the region within the pixel electrode that will appear as a darkline even in the presence of an applied voltage.

In the device (21) of the present invention, to prevent the formation ofan abnormal domain in the liquid crystal and to align the liquid crystalin the desired direction, it is essential that any electrode having thesame potential as the pixel electrode be not formed in the slit portionof the pixel electrode. This prevents an abnormal domain from beingformed by an electric field arising from the electrode having the samepotential as the pixel electrode, and serves to alleviate the problemsof low brightness, slow response speed, and display unevenness caused bythe presence of an abnormal domain.

As described above, according to the present invention, in the liquidcrystal display device in which the photopolymerizable componentdispersed in the liquid crystal is photopolymerized while applying avoltage, thereby defining the direction in which the liquid crystalmolecules tilt in the presence of an applied voltage, it becomespossible to prevent the formation of abnormal domains in the liquidcrystal and align the liquid crystal in the desired direction, and theliquid crystal display device of the invention can thus achieve highdisplay quality.

The seventh aspect of the invention discloses the following methods asspecific implementations thereof.

1) The method described in above item (22), wherein the additionalultraviolet radiation is applied using ultraviolet light whosewavelength is different from that of the ultraviolet light used for thepolymerization of the monomer before the application of the additionalultraviolet radiation.

2) The method described in above item (22), wherein the ultravioletlight used in the additional ultraviolet radiation has a spectrum havinga maximum energy peak at 310 to 380 nm.

3) The method described in above item (22), wherein the ultravioletlight used in the additional ultraviolet radiation has a spectrum havinga maximum energy peak at 350 to 380 nm.

4) The method described in above item (22), wherein the ultravioletlight used in the additional ultraviolet radiation has a spectrum havinga maximum energy peak at 310 to 340 nm.

5) The method described in above item (22), wherein the additionalultraviolet radiation is applied for 10 minutes or longer.

6) The method described in above item (22), wherein substrate surfacesare treated for vertical alignment in accordance with a verticalalignment mode, and liquid crystals in a non-display area also aresubstantially vertically aligned.

In the method of the present invention, after performing thepolymerization step for alignment control, additional ultravioletradiation is applied as an aftertreatment to react residual monomers.The additional radiation is performed by only radiating ultravioletlight to the liquid crystal component, without driving the liquidcrystal panel. The radiation should be applied for a relatively longtime by using light that efficiently emits ultraviolet light only of awavelength necessary for polymerization (i.e., the light that does notcontain visible light components, etc.) and whose intensity is not verystrong. Generally, a radiation time of 10 minutes to 24 hours ispreferred, though it depends on the intensity of the ultraviolet lightused. In this method, since the radiated light contains hardly anywavelength components longer than the ultraviolet light, the radiationdoes not cause a temperature rise and it becomes possible to radiatelight at an effective wavelength with a relatively strong intensity. Asa result, residual monomers can be polymerized without causing atemperature rise, and a panel virtually free from image sticking can beachieved. Furthermore, since the additional ultraviolet radiation doesnot require driving the panel but can be implemented using a simpleapparatus, many such radiation apparatuses can be installed so that manypanels can be treated at the same time even when radiation takes a longtime; accordingly, the additional ultraviolet radiation does not affectthe overall time of the panel fabrication process and degrade theproductivity.

EMBODIMENTS

The first aspect of the invention will be described further withreference to specific embodiments thereof.

Embodiment 1

As shown in FIG. 9, gate bus lines and data bus lines are arranged in anmatrix array on a first substrate, and the respective bus lines arebundled at one end. A TFT is located at each intersection of the buslines, and a pixel electrode is formed via the TFT. On a secondsubstrate on the opposite side is formed a common electrode which formsan electrical capacitance to each of the pixel electrodes, and a pad forapplying a voltage to it is drawn out in the lower left corner.

The pixel electrodes also form a layer called a Cs bus line and anauxiliary capacitance Cs within the first substrate. It can be said thatthe Cs bus line is another common electrode. The Cs bus line is drawnout as a pad (Cs) in the upper right corner.

The cross section of the thus constructed liquid crystal panel is thesame as that shown in FIG. 2; here, the first substrate corresponds tothe bottom substrate and the second substrate to the substrate on whichcolor filters are deposited.

On the surface of each substrate is formed an alignment film thatdetermines the initial alignment of the liquid crystal (the liquidcrystal alignment before the liquid crystal is exposed to lightradiation); in the illustrated example, a polyimide alignment filmexhibiting vertical alignment is used.

Here, a liquid crystal material that has a negative dielectricanisotropy Δ∈ of −3 to −5, and to which a trace amount (0.1 to 1.0%) ofliquid crystalline acrylic material exhibiting photosensitivity has beenadded, is used as the liquid crystal.

In the thus constructed liquid crystal panel, when an AC voltage(rectangular wave) of ±20 V is applied to the common electrode pad (C)and 0 V to the pad (Cs), the voltage applied to the liquid crystal part,as earlier described, is given byZ1c/(Z1c+Zc)×AC voltageIf the liquid crystal capacitance C1c=250 fF and the auxiliarycapacitance Cs=250 fF, then it can be seen from calculation that avoltage of about ±10 V has been applied to the liquid crystal part. WhenUV radiation is applied to the liquid crystal panel in this condition,the liquid crystalline acrylic material polymerizes by tilting in thedirection in which the liquid crystal molecules are tilted.

By removing the applied voltage after the radiation, a condition inwhich the initial alignment is slightly tilted from the verticalalignment can be achieved. The display characteristics of the completedpanel are shown in FIGS. 10 and 11; as can be seen, the characteristicsare influenced by the voltage applied when polymerizing the liquidcrystalline acrylic material, and when the AC voltage (rectangular wave)of ±20 V is applied, a panel having a white brightness of 320 cd/m² anda black brightness of 0.53 cd/m² (backlight of 5000 cd/m²) can beobtained.

Embodiment 2

Compared with the structure of the first embodiment shown in FIG. 1, thecommon electrode and the Cs bus line are completely insulated from eachother in the structure shown in FIG. 12 (generally, they areshort-circuited using conductive particles or silver paste). It ispreferable to completely insulate the common electrode from the Cs busline as illustrated here, because deterioration of the applied ACvoltage can then be alleviated.

In particular, the resistance per Cs bus line is often of the order ofseveral thousand ohms and, depending on the magnitude of leakage, theapplied voltage drops.

Embodiment 3

As described, above, it is desirable that the common electrode and theCs bus line be electrically insulated from each other, considering thevoltage application when exposing the liquid crystal to radiation. Thismethod, however, requires that a separate pattern from the voltagesupply pattern to the Cs bus line be formed for the common electrodethat needs to be supplied with currents from the four sides.

In view of this, if the common electrode is shorted to the Cs bus lineafter the radiation, as shown in the example shown here, supply ofcurrents from the four sides can be easily accomplished.

More specifically, as shown in the example of FIG. 13, portions that canbe shorted using a laser are provided in advance within the panelstructure. For this purpose, it is generally practiced to electricallyconnect the top and bottom substrates by using silver paste orconductive spacer means.

On the other hand, in the example shown in FIG. 14, the connection ismade at the terminal side. In the example shown here, the connectionbetween the common electrode and the Cs bus line is made outside thepanel.

Embodiment 4

In a liquid crystal panel having the structure shown in FIG. 15 which issimilar to that of the first embodiment, an AC voltage (rectangularwave) of ±8 V is applied to the common electrode pad (C) and 0 V to thepad (Cs), and further, −5 V is applied to the gate bus line.

As earlier described, the voltage applied to the liquid crystal part isgiven byZ1c/(Z1c+Zc)×AC voltage

With the voltage applied to the gate bus line, the current that flowsfrom the transistor to the data bus line can be suppressed.

As in the first embodiment, when UV radiation is applied to the liquidcrystal panel, the liquid crystalline acrylic material polymerizes bybeing dragged in the direction in which the liquid crystal molecules aretilted.

Embodiment 5

The foregoing embodiments have been described specifically dealing withthe case of the liquid crystal to which a liquid crystalline acrylicmaterial has been added. It will, however, be recognized that any of themethods described in the above embodiments can be applied to a panel,such as a polymer-dispersed liquid crystal display panel, that containsa photosensitive material, or to ferroelectric panel that needstreatment for alignment.

Embodiment 6

In the method of the first embodiment, if the frequency of the ACvoltage applied is high, the high resistance of the Cs bus line becomesa problem, and insufficient writing results. Conversely, if thefrequency is low, voltage leaks occur at high resistance connectionportions, resulting in an inability to write a uniform voltage over theentire surface of the panel. Considering that the wiring resistancevaries depending on the material, etc., the relationship between thefrequency and brightness was measured while varying the applied ACvoltage. The results are shown in FIG. 16. As can be seen, it ispreferable to set the AC frequency of the AC voltage within the range ofabout 1 Hz to 1 kHz.

Embodiment 7

This embodiment concerns an example in which a wiring defect is madeinvisible by applying a DC voltage while holding the wiring lines andelectrodes on the second substrate at the same potential.

In this example, the DC voltage is applied between the common electrodeand the three bus lines. Here, 10 V is applied to the common electrode,and 0 V is applied to the three bus lines. Then, as the voltage actuallyapplied to the liquid crystal is the same as the model explained in thedescription of the first embodiment, a panel having substantially thesame display characteristics (white brightness of 320 cd/m² and blackbrightness of 0.53 cd/m²) can be obtained. Needless to say, in thiscase, shorts between the bus lines, etc. do not present any problembecause they are held at the same voltage.

Embodiment 8

This embodiment is the same as the seventh embodiment, except that thedata bus lines are bundled at the opposite ends as well, as shown inFIG. 18. With this arrangement, if there is a break in a data bus line,the voltage can be supplied from the opposite end. In this case, thebundled portion should be separated afterwards by cutting the glass.

Embodiment 9

One method of avoiding the cutting process in the eighth embodiment isto connect the data bus lines via high resistance at the opposite end asshown in FIG. 19, instead of bundling them together. In the case of a DCvoltage, if a sufficient time elapses, the potential can be equalizeddespite the presence of high resistance connections, as explained inconnection with FIG. 5. Using this, it is also possible to apply a Dcvoltage by forming a pattern such as shown in FIG. 20 or 21.

In FIG. 20, the data bus lines, the gate bus lines, the Cs bus lines(including the repair line described later), and the common electrodeare all connected via high resistance such as ESD circuits. In thisexample, radiation is applied to the liquid crystal while applying 10 Vto the data bus lines, 10 V to the gate bus lines (including the repairline described later), and 0 V to the common electrode.

In FIG. 21, the data bus lines, the gate bus lines, and the Cs bus lines(including the repair line described later) are all connected via highresistance such as ESD circuits. However, these bus lines are insulatedfrom the common electrode. In this example, radiation is applied to theliquid crystal while applying 10 V to the data bus lines, and 0 V to thecommon electrode.

In each of the examples of FIGS. 20 and 21, the bus lines on the secondsubstrate are all held at the same potential.

Embodiment 10

In this embodiment, voltages are applied not only to the data bus lines,gate bus lines, Cs bus lines, and common electrode, but also to therepair line, as shown in FIG. 22.

The repair line is usually formed at both ends of the data bus lines orat the end opposite from the signal input end. In the device shown inthe figure, the repair line is located at the end opposite from thesignal input end.

In a typical example of repair, any defect, including a line defectcaused by an interlayer short, is converted to a defect of type b (databus line breakage), as explained with reference to FIG. 7, and thedefective line is connected to the repair line, as shown in FIG. 20. Inthis case, since the voltage from the signal input end does notpropagate beyond the broken point, the voltage may be rerouted via anESD circuit or the like within the panel, as in other embodimentsearlier described, but compared with that method, applying a voltagedirectly to the repair line is a much more reliable method.

Based on the above concept, in the device of FIG. 22, a voltage isapplied to the repair line directly or via a high resistance connection.In the figure, the bus lines and the TFTs are arranged on the secondsubstrate. A transparent electrode as the common electrode is formed onthe first substrate. An alignment film is formed on each substrate byprinting, spinning, or other techniques. Liquid crystal with a traceamount of liquid crystalline acrylic material added to it is sandwichedbetween the two substrates.

Next, 0 V is applied to the common electrode, while a DC voltage of 10 Vis applied to the portions connected via high resistance to the gate buslines, data bus lines, and repair line. After applying the voltage tothe liquid crystal in this way, UV radiation is applied to the liquidcrystal part.

Embodiment 11

This embodiment concerns an example in which a CF-ON-TFT structure isemployed as the panel structure, as shown in FIG. 23. As previouslyshown in FIG. 4, a shift in TFT threshold value occurs when ultravioletradiation is directly applied when the TFTs are ON. When color filtersare formed on the TFT substrate in such a manner as to cover the TFTs,most of the ultraviolet radiation falling on the substrate can be cutoff, as a result of which shifting in the threshold value can besuppressed.

In FIG. 23, the TFTs are arranged on the second substrate, and the colorfilters are formed over the TFTs, on top of which pixel electrodes areformed. A transparent electrode as the common electrode is formed on thefirst substrate. An alignment film is formed on each substrate byprinting, spinning, or other techniques. Liquid crystal with a traceamount of liquid crystalline acrylic material added to it is sandwichedbetween the two substrates.

Next, 0 V is applied to the common electrode and 20 V to the gate buslines, while an 30-Hz AC square wave voltage of ±10 V is applied to thedata bus lines. The data bus lines are bundled at both ends, as shown inFIG. 18.

After applying the voltage to the liquid crystal in this way, UVradiation is applied from the first substrate side.

Embodiment 12

This embodiment concerns an example in which not only is a lightblocking film formed on the TFTs in order to suppress the shifting inTFT threshold, but the same signal as input to the data bus lines isapplied to the repair line, as shown in FIG. 24, in order to apply avoltage uniformly to a line defect portion as well. As in the 11thembodiment, the TFTs are arranged on the second substrate, and the colorfilters are formed over the TFTs, on top of which pixel electrodes areformed. A transparent electrode as the common electrode is formed on thefirst substrate. An alignment film is formed on each substrate byprinting, spinning, or other techniques. Liquid crystal with a traceamount of liquid crystalline acrylic material added to it is sandwichedbetween the two substrates.

Next, 0 V is applied to the common electrode and 20 V to the gate buslines, while an 30-Hz AC square wave voltage of ±10 V is applied to therepair line as well as to the data bus lines. Here, the repair line isconnected to the bus line to be repaired.

After applying the voltage to the liquid crystal in this way, UVradiation is applied from the first substrate side.

Next, the second aspect of the invention will be described withreference to specific embodiments thereof. In each of the followingembodiments, the display device uses vertical alignment films and aliquid crystal material having a negative dielectric anisotropy, andsince the polarizers are arranged in a crossed Nicol configuration andattached to both sides of the liquid crystal panel, the display deviceis normally black. The polarization axis of each polarizer is orientedat 45° to the bus lines. The panel size is 15 inches in diagonal, andthe resolution is XGA. Liquid crystalline acrylate monomer UCL-001manufactured by Dainippon Ink and Chemicals, Inc. was used as thepolymerizable monomer, and a liquid crystal material having negative Δ∈was used as the liquid crystal.

Embodiment 13

A liquid crystal panel having an ITO pattern such as shown in FIG. 25was fabricated.

Since the gap between the data bus line and the ITO is approximatelyequal to the width of each fine ITO slit, liquid crystal molecules tiltin the direction parallel to the data bus line even in the portioncorresponding to the gap between the data bus line and the ITO, that is,all the liquid crystal molecules tilt in the same direction, preventingthe formation of dark areas. To achieve symmetrical viewing anglecharacteristics, the area where the liquid crystal molecules tilt towardthe top of FIG. 23 and the area where the liquid crystal molecules tilttoward the bottom of FIG. 25 are substantially equal in size.

In FIG. 25, the fine electrodes are connected together at the center ofthe pixel. As shown in FIG. 26 which is a cross-sectional view showingone example of the device of FIG. 25, the direction in which the liquidcrystal molecules tilt can be controlled by an electric field alone, butas shown in FIG. 27 which is a cross-sectional view showing anotherexample of the device of FIG. 25, protruding banks may be formed inorder to more clearly define the direction in which the liquid crystalmolecules tilt. Instead of providing the banks, the alignment film maybe rubbed in the direction shown, or an optical alignment technique maybe used.

A voltage 0.1 V higher than the threshold voltage was applied to theliquid crystal composition filled into the panel, and one minute wasallowed to pass; then, after confirming by observation under amicroscope that the alignment had been controlled in the desireddirection, the voltage was raised to 3 V at a rate of 0.01 V per second,and then to 10 V at a rate of 0.1 V per second, and with the voltage of10 V applied, ultraviolet radiation was applied to polymerize themonomer. The fabrication of a liquid crystal panel free from alignmentdisruptions was thus achieved.

Embodiment 14

A liquid crystal panel having an ITO pattern such as shown in FIG. 28was fabricated.

A voltage 0.1 V higher than the threshold voltage was applied to theliquid crystal composition filled into the panel, and one minute wasallowed to pass to allow the alignment of the liquid crystal moleculesto stabilize; after that, the voltage was raised to 3 V at a rate of0.01 V per second, and then to 10 V at a rate of 0.1 V per second, andwith the voltage of 10 V applied, ultraviolet radiation was applied topolymerize the monomer. The fabrication of a liquid crystal panel freefrom alignment disruptions was thus achieved.

Next, the third aspect of the invention will be described with referenceto specific embodiments thereof.

Embodiments 15 to 17 and Comparative Examples 1 and 2

Embodiments of the present invention, each using a 15-inch XGA-LCD, areshown in FIG. 33 for comparison with comparative examples fabricatedaccording to the prior art method. An N-type liquid crystal materialhaving negative Δ∈ was used as the liquid crystal. Liquid crystallineacrylate monomer UCL-001 manufactured by Dainippon Ink and Chemicals,Inc. was used as the polymerizable monomer. The concentration of themonomer in the liquid crystal composition was 0.1 to 2% by weight. Aphotopolymerization initiator was added at a concentration of 0 to 10%relative to the weight of the monomer. The UV radiation conditions andthe obtained results are shown in Table 1.

TABLE 1 RA- DIA- TION 1ST UV RADIATION 2ND UV RADIATION 3RD UV RADIATIONTIME UV AMOUNT UV AMOUNT UV AMOUNT WITH INTEN- OF UV INTEN- OF UV INTEN-OF UV AP- VOLT- SITY RADIA- VOLT- SITY RADIA- VOLT- SITY RADIA- PLIEDAGE (mW/ TION AGE (mW/ TION AGE (mW/ TION BURN- CON- VOLT- EXAMPLE NO.Run (V) cm²) (mJ/cm²) (V) cm²) (mJ/cm²) (V) cm²) (mJ/cm²) IN TRAST AGEEMBODIMENT {circle around (1)} 10 100 4000 0 10 4000 — — — 7% 600 40 15{circle around (2)} 10 100 4000 0 10 6000 — — — 6% 600 40 {circle around(3)} 10 100 4000 0 10 8000 — — — 6% 600 40 {circle around (4)} 10 102000 0 100 4000 — — — 8% 700 200 {circle around (5)} 10 10 2000 0 1006000 — — — 7% 700 200 {circle around (6)} 10 10 2000 0 100 8000 — — — 7%700 200 EMBODIMENT {circle around (7)} 0 10 500 10 100 4000 — — — 9% 70040 16 {circle around (8)} 0 10 1000 10 100 4000 — — — 9% 700 40EMBODIMENT {circle around (9)} 0 10 500 10 100 4000 0 10 4000 7% 700 4017 {circle around (10)}  0 10 500 10 100 4000 0 10 6000 6% 700 40{circle around (11)}  0 10 500 10 100 4000 0 10 8000 6% 700 40COMPARATIVE 10 10 4000 — — — — — — 18% 600 400 EXAMPLE 1 COMPARATIVE 1010 8000 — — — — — — 6% 300 800 EXAMPLE 2

In the first comparative example, the applied voltage during UVradiation was 10 V, the UV intensity was 10 mW/cm², and the amount ofradiation was 4000 mJ/cm². The radiation time was about 400 seconds, anda contrast of about 600 was obtained, but residual monomers were leftand the image sticking was as large as 18%. When the amount of UVradiation was increased to 8000 mJ/cm², as in the second comparativeexample, the image sticking decreased to 6%; however, in this case, thecontrast decreases, and the radiation time becomes as long as about 800seconds.

The method of the 15th embodiment is a method in which a voltage of 10 Vis applied during the first radiation to provide a desired pretilt, andthe second radiation is performed without applying an electric field toeliminate residual monomers. As shown in Table 1, the first radiationwas performed by applying high intensity UV in some examples and lowintensity UV in others; in the case of the high intensity UV radiation(100 mW/m²), the radiation time, with an applied voltage, was about 40seconds, and good results were obtained for both the image sticking andthe contrast. On the other hand, in the case of the low intensity UVradiation (10 mW/m²), the radiation time, with an applied voltage,increased up to 200 seconds, but it was not longer than one half thetime required in the comparative examples, and good results wereobtained for both the image sticking and the contrast.

In the method of the 16th embodiment, the first radiation is performedwithout applying an electric field, but the second radiation isperformed while applying a voltage. More specifically, the firstradiation is performed by applying a small amount of radiation to causethe monomers to react to a certain extent, thereby making the monomersin unradiated areas easier to react and, thereafter, UV radiation isapplied in the presence of an applied voltage. Since post-radiation isnot performed, the image sticking somewhat increases, but the contrastis further improved.

In the method of the 17th embodiment, both the post-radiation andpre-radiation are performed. Good results were obtained for both theimage sticking and the contrast.

Next, the fourth aspect of the invention will be described withreference to specific embodiments thereof.

Embodiment 18

TFT devices, data bus lines, gate bus lines, and pixel electrodes wereformed on one substrate. A color layer and a common electrode wereformed on the other substrate. An empty cell was fabricated bylaminating the two substrates together with 4-μm diameter spacersinterposed therebetween. An acrylic photopolymerizable componentexhibiting the nematic liquid crystalline state was mixed in an amountof 0.3 weight percent into a negative-type liquid crystal material, andthe thus prepared liquid crystal composition containing thephotopolymerizable component was injected into the cell to fabricate aliquid crystal panel. As shown in FIG. 34, the panel was provided withthree injection ports which were formed in positions 68 mm to 80 mm, 110mm to 122 mm, and 152 mm to 164 mm, respectively, on a 232-mm long side.

A gate voltage of 30 VDC, a data voltage of 10 VDC, and a common voltageof 5 VDC were applied to the panel to cause the liquid crystal moleculesin the panel to tilt, and in this condition, 300-nm to 450-nmultraviolet radiation of 2000 mJ/cm² was applied from the commonsubstrate side. The ultraviolet polymerizable monomer was thuspolymerized. Next, polarizers were attached to complete the fabricationof the liquid crystal panel. It was confirmed that the thus fabricatedliquid crystal panel achieved a high display quality free from displaydefects such as display unevenness in the corners.

Embodiment 19

TFT devices, data bus lines, gate bus lines, and pixel electrodes wereformed on one substrate. A color layer and a common electrode wereformed on the other substrate. An empty cell was fabricated bylaminating the two substrates together with 4-μm diameter spacersinterposed therebetween. An acrylic photopolymerizable componentexhibiting the nematic liquid crystalline state was mixed in an amountof 0.3 weight percent into a negative-type liquid crystal material, andthe thus prepared liquid crystal composition containing thephotopolymerizable component was injected into the cell to fabricate aliquid crystal panel. As shown in FIG. 35, the BM portion of the panelframe edge was formed by laminating CF resin layers; the cell gap atthis portion was 2.4 μm (the cell gap in the display area was 4.0 μm)and the distance to the seal was 0.2 mm.

A gate voltage of 30 VDC, a data voltage of 10 VDC, and a common voltageof 5 VDC were applied to the panel to cause the liquid crystal moleculesin the panel to tilt, and in this condition, 300-nm to 450-nmultraviolet radiation of 2000 mJ/cm² was applied from the commonsubstrate side. The ultraviolet polymerizable monomer was thuspolymerized. Next, polarizers were attached to complete the fabricationof the liquid crystal panel. It was confirmed that the thus fabricatedliquid crystal panel achieved a high display quality free from displaydefects such as display unevenness in the corners.

In the above structure, it will be appreciated that the same effect canbe obtained if a CF resin film is deposited on a metal BM of Cr or thelike instead of forming the panel BM portion by laminating the resinlayers.

Embodiment 20

TFT devices, data bus lines, gate bus lines, and pixel electrodes wereformed on one substrate. A color layer and a common electrode wereformed on the other substrate. An empty cell was fabricated bylaminating the two substrates together with 4-μm diameter spacersinterposed therebetween. An acrylic photopolymerizable componentexhibiting the nematic liquid crystalline state was mixed in an amountof 0.3 weight percent into a negative-type liquid crystal material, andthe thus prepared liquid crystal composition containing thephotopolymerizable component was injected into the cell to fabricate aliquid crystal panel. As shown in FIG. 36, an auxiliary seal was formedon the BM portion of the panel frame edge, to eliminate the cell gap atthe BM portion of the frame edge.

A gate voltage of 30 VDC, a data voltage of 10 VDC, and a common voltageof 5 VDC were applied to the panel to cause the liquid crystal moleculesin the panel to tilt, and in this condition, 300-nm to 450-nmultraviolet radiation of 2000 mJ/cm² was applied from the commonsubstrate side. The ultraviolet polymerizable monomer was thuspolymerized, and a polymer network was formed within the panel. Next,polarizers were attached to complete the fabrication of the liquidcrystal panel. It was confirmed that the thus fabricated liquid crystalpanel achieved a high display quality free from display defects such asdisplay unevenness in the corners.

Embodiment 21

TFT devices, data bus lines, gate bus lines, and pixel electrodes wereformed on one substrate. A color layer and a common electrode wereformed on the other substrate. An empty cell was fabricated bylaminating the two substrates together with 4-μm diameter spacersinterposed therebetween. An acrylic photopolymerizable componentexhibiting the nematic liquid crystalline state was mixed in an amountof 0.3 weight percent into a negative-type liquid crystal material, andthe thus prepared liquid crystal composition containing thephotopolymerizable component was injected into the cell to fabricate aliquid crystal panel. As shown in FIG. 37, pockets were formed in the BMportion of the panel frame edge by using auxiliary seals, to allowliquid crystals of abnormal concentrations to enter these pockets.

A gate voltage of 30 VDC, a data voltage of 10 VDC, and a common voltageof 5 VDC were applied to the panel to cause the liquid crystal moleculesin the panel to tilt, and in this condition, 300-nm to 450-nmultraviolet radiation of 2000 mJ/cm² was applied from the commonsubstrate side. The ultraviolet polymerizable monomer was thuspolymerized. Next, polarizers were attached to complete the fabricationof the liquid crystal panel. It was confirmed that the thus fabricatedliquid crystal panel achieved a high display quality free from displaydefects such as display unevenness in the corners.

Next, the fifth aspect of the invention will be described with referenceto specific embodiments thereof.

Embodiment 22

A cross-sectional view of the panel of this embodiment is shown in FIG.38. The layer structure of the TFT substrate comprises, from the bottomto the top, a gate metal layer of Al—Nd/MoN/Mo, a gate insulating filmof SiN, an a-Si layer, a drain metal layer of n+/Ti/Al/MoN/Mo, aprotective film layer of SiN, and a pixel electrode layer of ITO. Thestructure of the CF substrate comprises a color filter layer of red,blue, and green and an ITO film layer that forms the common electrode.FIG. 39 shows a plan view of this panel. According to this pixelelectrode pattern, when a voltage is applied, liquid crystal moleculestilt in four different directions a, b, c, and d, as shown in thefigure. This achieves a wide viewing angle. The common electrode made ofITO is formed on one of the opposing substrates. A vertical alignmentfilm was deposited on each of the two substrates, spacer beads wereapplied to one of the substrates, a panel periphery seal was formed onthe other substrate, and the two substrates were laminated together.Liquid crystal was injected into the thus fabricated panel. Anegative-type liquid crystal material having a negative dielectricanisotropy, with 0.2 weight percent of ultraviolet curable monomer addedto it, was used as the liquid crystal. Ultraviolet radiation was appliedto the panel, in the presence of an applied voltage, to control thealignment of the liquid crystal. FIG. 40 shows how the liquid crystalalignment is controlled by the polymer. In the initial state where novoltage is applied, the liquid crystal molecules are aligned vertically,and monomers exist as monomers. When a voltage is applied, the liquidcrystal molecules tilt in the directions defined by the fine pattern ofthe pixel electrode, and the monomers tilt in like manner. Whenultraviolet radiation is applied in this condition, the tilted monomersare polymerized, thus controlling the alignment of the liquid crystalmolecules.

Voltage application and ultraviolet radiation patterns such as shown inFIG. 41 can be employed here. In the figure, high intensity ultravioletradiation refers to the radiation of 300-nm to 450-nm ultraviolet lightwith an intensity of 30 mW or higher, and low intensity ultravioletradiation refers to the ultraviolet radiation with an intensity of 30 mWor lower. Further, a high voltage means a voltage applied to the liquidcrystal layer that is equal to or greater than the threshold voltage ofthe liquid crystal, and low voltage means a voltage that is equal to orlower than the threshold voltage of the liquid crystal, or means noapplication of voltage.

The thus fabricated liquid crystal panel was a high quality panel havinghigh brightness and wide viewing angle and free from image sticking.

Embodiment 23

To implement the panel fabrication method of the 22nd embodiment,manufacturing equipment comprising two ultraviolet radiation unitsconnected together was used as shown in FIG. 42; here, the first unitcan radiate ultraviolet light while applying a voltage, and the secondunit has a structure that applies ultraviolet radiation to the panelwhile transporting the panel on transport rollers. With this equipment,a high throughput, space-saving fabrication of the panel can beachieved.

Embodiment 24

A cross-sectional view of the panel of this embodiment is shown in FIG.43. A color filter layer and an overcoat layer are formed over the TFTarray, and high transmittance of light can be achieved with thisstructure.

Next, the sixth aspect of the invention will be described with referenceto specific embodiments thereof.

Embodiment 25

TFT devices, data bus lines, gate bus lines, and pixel electrodes wereformed on one substrate. A color layer and a common electrode wereformed on the other substrate. An empty cell was fabricated bylaminating the two substrates together with 4-μm diameter spacersinterposed therebetween. An acrylic photopolymerizable componentexhibiting the nematic liquid crystalline state was mixed in an amountof 0.3 weight percent into a negative-type liquid crystal material, andthe thus prepared liquid crystal composition containing thephotopolymerizable component was injected into the cell to fabricate aliquid crystal panel. FIG. 45 shows a plan view and a cross-sectionalview of a pixel in the thus fabricated panel; as shown, the sourceelectrode/pixel electrode contact hole and the Cs intermediateelectrode/pixel electrode contact hole are both located at a liquidcrystal domain boundary formed by pixel slits. This structure serves toprevent the formation of abnormal domains resulting from the contactholes, and the thus fabricated liquid crystal display device does notcontain any abnormal domains and has a high display quality free fromdisplay unevenness and degradations in brightness and response speedcharacteristics.

Embodiment 26

TFT devices, data bus lines, gate bus lines, and pixel electrodes wereformed on one substrate. A color layer, a common electrode, andalignment controlling banks were formed on the other substrate. An emptycell was fabricated by laminating the two substrates together with 4-μmdiameter spacers interposed therebetween. An acrylic photopolymerizablecomponent exhibiting the nematic liquid crystalline state was mixed inan amount of 0.3 weight percent into a negative-type liquid crystalmaterial, and the thus prepared liquid crystal composition containingthe photopolymerizable component was injected into the cell to fabricatea liquid crystal panel. FIG. 46 shows a plan view of a pixel in the thusfabricated panel; as shown, the source electrode/pixel electrode contacthole and the Cs intermediate electrode/pixel electrode contact hole areboth located at the crossing portions of the banks which correspond tothe boundaries of the liquid crystal domains. The portions of the sourceelectrode and the Cs intermediate electrode which are extended into thedisplay area run along the liquid crystal domain boundaries deliberatelyformed by the pixel electrode slits, and these portions do not causeabnormal domains, nor do they lower the numerical aperture. The thusfabricated liquid crystal display device does not contain any abnormaldomains and has a high display quality free from display unevenness anddegradations in brightness and in response speed characteristics.

Embodiment 27

A liquid crystal panel was fabricated in the same manner as in the 25thembodiment. FIG. 47 shows a plan view of a pixel; as shown, the sourceelectrode/pixel electrode contact hole and the Cs intermediateelectrode/pixel electrode contact hole are located in differentalignment sub-regions, and if any of them becomes a starting point of anabnormal domain, it will not cause interactions that could lead to theformation of an abnormal domain over a wider area. The thus fabricatedliquid crystal display device contains few abnormal domains and has ahigh display quality virtually free from display unevenness anddegradations in brightness and in response speed characteristics.

Embodiment 28

TFT devices, data bus lines, gate bus lines, a color layer, and pixelelectrodes were formed on one substrate. A common electrode was formedon the other substrate. An empty cell was fabricated by laminating thetwo substrates together with 4-μm diameter spacers interposedtherebetween. An acrylic photopolymerizable component exhibiting thenematic liquid crystalline state was mixed in an amount of 0.3 weightpercent into a negative-type liquid crystal material, and the thusprepared liquid crystal composition containing the photopolymerizablecomponent was injected into the cell to fabricate a liquid crystalpanel. FIG. 48 shows a plan view and a cross-sectional view of a pixelin the thus fabricated panel; as shown, a contact hole where cellthickness varies, which could cause an abnormal domain, is located at aliquid crystal domain boundary. Further, the pixel electrode, the sourceelectrode, and the Cs intermediate electrode are connected via onecontact hole and, thus, the cause of abnormal domains is eliminated andthe numerical aperture increased. The source electrode is wired along aliquid crystal domain boundary deliberately formed by pixel electrodeslits and located outside the pixel slit area, and this therefore doesnot cause an abnormal domain, nor does it lower the numerical aperture.The thus fabricated liquid crystal display device does not contain anyabnormal domains and has a high display quality free from displayunevenness and degradations in brightness and response speedcharacteristics.

Next, the seventh aspect of the invention will be described withreference to specific embodiments thereof.

Embodiment 29

A panel comprising a TFT substrate and a color filter substrate, with avertically aligned liquid crystal of negative Δ∈ sandwiched between thetwo substrates, was used. Liquid crystalline acrylate monomer UCL-001manufactured by Dainippon Ink and Chemicals, Inc. was added in an amountof 0.25 weight percent into the liquid crystal layer. While driving theliquid crystal by applying a drive voltage having an effective value of5.0 V to the liquid crystal layer, ultraviolet light having a maximumenergy peak at wavelength 365 nm is projected for 300 seconds to thepanel, thereby polymerizing and curing the monomer in a prescribedliquid crystal alignment state. A polyamic acid alignment filmexhibiting vertical alignment was used here. The panel cell gap was setat 4.0 μm. The liquid crystal driving mode was normally black mode.

Next, as shown in FIG. 49, additional ultraviolet radiation was appliedto the panel. Commercially available black lamps (manufactured byToshiba Lighting and Technology Corporation) were used as the lightsource for the additional radiation. The maximum energy peak wavelengthwas 352 nm, and five lamps were arranged, spaced 10 cm apart from eachother, to form a surface-area light source, and light was radiated froma distance of 10 cm with an intensity of 5 mW/cm². When the imagesticking ratio of the panel was measured before and after the additionalultraviolet radiation, the image sticking ratio of the panel before theadditional ultraviolet radiation was 12%, while the image sticking ratioof the panel after the radiation was reduced to 3%. When the testedpanels were left idle for 24 hours, the former was never restored to theoriginal condition, but in the latter, the image sticking was completelyerased.

Further, the relationship between the amount of ultraviolet radiationand the image sticking ratio was obtained by varying the amount ofadditional ultraviolet radiation to be applied to the panel. The resultis shown in FIG. 50. As can be seen, the image sticking ratio reduces asthe amount of ultraviolet radiation increases.

Here, the image sticking ratio was obtained in the following manner. Ablack and white checkered pattern was displayed for 48 hours in thedisplay area. After that, prescribed halftone dots (gray) were displayedover the entire display area, and the difference between the brightnessβ of the area that was displayed in white and the brightness γ of thearea that was displayed in black (β−γ) was divided by the brightness γof the area that was displayed in black, to obtain the image stickingratio.Image sticking ratio α=((β−γ)/γ)×100(%)

Embodiment 30

The process described in the 29th embodiment was repeated with thedifference that commercially available UV-B fluorescent lamps(manufactured by Tozai Densan, Ltd.) ware used instead of the blacklamps. The maximum energy peak frequency of this fluorescent lamp was310 nm. In the panel subjected to the additional ultraviolet radiationof this embodiment, the image sticking ratio was reduced to 2.5%, andwhen the panel was left idle for 24 hours, the image sticking wascompletely erased.

The fabrication method for the liquid crystal display device accordingto the first aspect of the invention described above can be summarizedas follows:

(Item 1)

A method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance to the pixel electrode;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween; and

radiating light onto the liquid crystal layer while applying an ACvoltage between the common electrode and the pixel electrode by applyingAC voltages to the common electrode and the Cs bus line.

(Item 2)

A method of fabricating a liquid crystal display device as described initem 1, wherein the common electrode and the Cs bus line are insulatedfrom each other or connected via high resistance when radiating thelight onto the liquid crystal layer.

(Item 3)

A method of fabricating a liquid crystal display device as described initem 1, wherein after radiating the light onto the liquid crystal layer,the common electrode and the Cs bus line are electrically connectedtogether.

(Item 4)

A method of fabricating a liquid crystal display device as described initem 1 wherein, initially, the liquid crystal layer is verticallyaligned and, by radiating the light while applying a voltage to theliquid crystal composition containing the photosensitive material, theaverage angle of the liquid crystal to an alignment film is set smallerthan a polar angle of 90°.

(Item 5)

A method of fabricating a liquid crystal display device as described initem 1, wherein AC frequency when applying the AC voltage is set withina range of 1 to 1000 Hz.

(Item 6)

A method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance with the pixel electrode;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance using the common electrode and thepixel electrode by sandwiching the liquid crystal layer therebetween;

insulating the common electrode from the three bus lines, or connectingthe common electrode to the three bus lines via high resistance; and

radiating light to the liquid crystal layer while applying a DC voltagebetween the common electrode and the pixel electrode by applying a DCvoltage between the common electrode and the three bus lines (the gatebus line, the data bus line, and the Cs bus line) formed on the secondsubstrate.

(Item 7)

A method of fabricating a liquid crystal display device as described initem 1, wherein adjacent gate bus lines or data bus lines areelectrically connected together at both ends thereof.

(Item 8)

A method of fabricating a liquid crystal display device as described initem 7, wherein after radiating the light onto the liquid crystal layer,the common electrode and the Cs bus line are electrically connectedtogether.

(Item 9)

A method of fabricating a liquid crystal display device as described initem 6 wherein, initially, the liquid crystal layer is verticallyaligned and, by radiating the light while applying a voltage to theliquid crystal composition containing the photosensitive material, theaverage angle of the liquid crystal to an alignment film is set smallerthan a polar angle of 90°.

(Item 10)

A method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, a Cs bus line that forms an electrical capacitanceto the pixel electrode, and a repair line intersecting with at least oneof the data bus and gate bus lines;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween; and

radiating light to the liquid crystal layer while applying a DC voltagebetween the common electrode and the pixel electrode by applying a DCvoltage between the common electrode and the four bus lines (the gatebus line, the data bus line, the Cs bus line, and the repair line)formed on the second substrate.

(Item 11)

A method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance with the pixel electrode;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance using the common electrode and thepixel electrode by sandwiching the liquid crystal layer therebetween;and

connecting the common electrode via high resistance to the three buslines (the gate bus line, the data bus line, and the Cs bus line,)formed on the second substrate, and radiating light to the liquidcrystal layer while applying a DC voltage between the common electrodeand the pixel electrode by applying a DC voltage between the commonelectrode and at least one of the bus lines.

(Item 12)

A method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, and a Cs bus line that forms an electricalcapacitance to the pixel electrode;

forming a CF resin or a light blocking pattern on a channel portion ofthe thin-film transistor;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance using the common electrode and thepixel electrode by sandwiching the liquid crystal layer therebetween;

electrically connecting adjacent data bus lines at both ends thereof;and

radiating light onto the liquid crystal layer while applying an ACvoltage between the common electrode and the pixel electrode by applyinga transistor ON voltage to the gate bus line and an AC voltage betweenthe common electrode and the data bus line.

(Item 13)

A method of fabricating a liquid crystal display device, comprising:

forming on a first substrate a common electrode for applying a voltageover an entire surface of the substrate;

forming on a second substrate a gate bus line and a data bus linearranged in a matrix array, a thin-film transistor located at anintersection of the two bus lines, a pixel electrode connecting to thethin-film transistor, a Cs bus line that forms an electrical capacitanceto the pixel electrode, and a repair line intersecting with the data busline;

-   -   forming a CF resin or a light blocking pattern on a channel        portion of the thin-film transistor;

forming a liquid crystal layer by filling a liquid crystal composition,containing a photosensitive material, into a gap between the firstsubstrate and the second substrate;

forming an electrical capacitance by the common electrode and the pixelelectrode by sandwiching the liquid crystal layer therebetween;

connecting at least one data bus line with at least one repair line bylaser radiation or other method; and

radiating light onto the liquid crystal layer while applying an ACvoltage between the common electrode and the pixel electrode by applyinga transistor ON voltage to the gate bus line and an AC voltage betweenthe common electrode and the data bus line and repair line (the repairline is at the same potential as the data bus line).

(Item 14)

A liquid crystal display device fabricated by a method described in anyone of items 1 to 13.

The fabrication method for the liquid crystal display device accordingto the second aspect of the invention can be summarized as follows:

(Item 15)

A method of fabricating a vertical alignment liquid crystal displaydevice, comprising:

forming a liquid crystal layer by filling a liquid crystal compositioninto a gap between two substrates each having a transparent electrodeand an alignment control film for causing liquid crystal molecules toalign vertically, the liquid crystal composition having a negativedielectric anisotropy and containing a polymerizable monomer; and

polymerizing the monomer while applying a voltage between opposingtransparent electrodes, and thereby providing a pretilt angle to theliquid crystal molecules, and wherein:

before polymerizing the monomer, a constant voltage not smaller than athreshold voltage but not greater than a saturation voltage is appliedbetween the opposing transparent electrodes for a predetermined periodof time and, thereafter, the voltage is changed to a prescribed voltageand, while maintaining the prescribed voltage, ultraviolet radiation orheat is applied to the liquid crystal composition to polymerize themonomer.

(Item 16)

A method of fabricating a liquid crystal display device as described initem 15, wherein after a constant voltage not smaller than the thresholdvoltage but not greater than the threshold voltage+1 V is appliedbetween the opposing transparent electrodes for a time not shorter than10 seconds, the voltage is changed by applying a voltage not smallerthan a voltage to be applied to produce a white display state and, whilemaintaining the voltage, the ultraviolet radiation or heat is applied tothe liquid crystal composition to polymerize the monomer.

(Item 17)

A method of fabricating a liquid crystal display device as described initem 15 or 16, further comprising the step of forming a slit structurein the transparent electrode on at least one of the substrates.

(Item 18)

A method of fabricating a liquid crystal display device as described inany one of items 15 to 17, further comprising the step of forming, on atleast one of the substrates, a protrusion protruding into the gapbetween the substrates.

(Item 19)

A liquid crystal display device fabricated by a method described in anyone of items 15 to 18.

The fabrication method for the liquid crystal display device accordingto the third aspect of the invention can be summarized as follows:

(Item 20)

A method of fabricating a liquid crystal display device, comprising:

forming a liquid crystal layer by filling a liquid crystal compositioncontaining a polymerizable monomer into a gap between two substrateseach having a transparent electrode; and

polymerizing the monomer while applying a voltage between opposingtransparent electrodes, and thereby providing a pretilt angle to liquidcrystal molecules while, at the same time, controlling the direction inwhich the liquid crystal molecules tilt in the presence of an appliedvoltage, and wherein:

light radiation for polymerizing the polymerizable monomer is performedin at least two steps.

(Item 21)

A method of fabricating a liquid crystal display device as described initem 20, wherein at least one of the plurality of light radiation stepsis performed while applying a voltage to the liquid crystal layer.

(Item 22)

A method of fabricating a liquid crystal display device as described initem 20 or 21, wherein the plurality of light radiation steps areperformed without applying a voltage, either before or after or bothbefore and after the light radiation that is performed in the presenceof an applied voltage.

(Item 23)

A method of fabricating a liquid crystal display device as described inany one of items 20 to 22, wherein the plurality of light radiationsteps are respectively performed with different light intensities.

(Item 24)

A method of fabricating a liquid crystal display device as described inany one of items 20 to 23, wherein the light radiation that is performedin the presence of an applied voltage is performed with a lightintensity of 50 mW/cm² or higher.

(Item 25)

A method of fabricating a liquid crystal display device as described inany one of items 20 to 24, wherein the light radiation that is performedwithout applying a voltage is performed with a light intensity of 50mW/cm² or lower.

(Item 26)

A method of fabricating a liquid crystal display device as described inany one of items 20 to 25, wherein the polymerizable monomer is a liquidcrystalline or non-liquid-crystalline monomer, and is polymerized byultraviolet radiation.

(Item 27)

A method of fabricating a liquid crystal display device as described inany one of items 20 to 26, wherein the polymerizable monomer isbifunctional acrylate or a mixture of bifunctional acrylate andmonofunctional acrylate.

(Item 28)

A liquid crystal display device fabricated by a method described in anyone of items 20 to 27.

The liquid crystal display device according to the fourth aspect of theinvention can be summarized as follows:

(Item 29)

A liquid crystal display device in which a liquid crystal compositioncontaining a photopolymerizable or thermally polymerizable component issandwiched between substrates and the polymerizable component ispolymerized while applying a voltage, thereby defining the direction inwhich liquid crystal molecules tilt in the presence of an appliedvoltage, wherein a plurality of injection ports for injectingtherethrough the liquid crystal composition containing the polymerizablecomponent are formed in one side of the liquid crystal display device,and spacing between the respective injection ports is not larger thanone-fifth of the length of the side in which the injection ports areformed.

(Item 30)

A liquid crystal display device as described in item 29, wherein theinjection ports are spaced away from a display edge by a distance notgreater than two-fifths of the length of the side in which the injectionports are formed.

(Item 31)

A liquid crystal display device in which a liquid crystal compositioncontaining a photopolymerizable or thermally polymerizable component issandwiched between substrates and the polymerizable component ispolymerized while applying a voltage, thereby defining the direction inwhich liquid crystal molecules tilt in the presence of an appliedvoltage, wherein a cell gap in a frame edge BM area is not larger thanthe cell gap of a display area.

(Item 32)

A liquid crystal display device as described in item 31, wherein thearea where the cell gap is not larger than the cell gap of the displayarea is spaced away from a cell forming seal by a distance not greaterthan 0.5 mm.

(Item 33)

A liquid crystal display device in which a liquid crystal Compositioncontaining a photopolymerizable or thermally polymerizable component issandwiched between substrates and the polymerizable component ispolymerized while applying a voltage, thereby defining the direction inwhich liquid crystal molecules tilt in the presence of an appliedvoltage, wherein a main seal or an auxiliary seal is formed in a frameedge BM area to eliminate cell gap in the frame edge BM area.

(Item 34)

A liquid crystal display device in which a liquid crystal compositioncontaining a photopolymerizable or thermally polymerizable component issandwiched between substrates and the polymerizable component ispolymerized while applying a voltage, thereby defining the direction inwhich liquid crystal molecules tilt in the presence of an appliedvoltage, wherein an auxiliary seal is formed so that a material whoseconcentration of the polymerizable material relative to liquid crystalis abnormal is guided into a BM area.

(Item 35)

A liquid crystal display device as described in any one of items 29 to34, wherein the liquid crystal composition contains a non-liquid-crystalcomponent or a component whose molecular weight and surface energy aredifferent from those of a liquid-crystal component.

The fabrication method for the liquid crystal display device accordingto the fifth aspect of the invention can be summarized as follows:

(Item 36)

A method of fabricating a liquid crystal display device, comprising:

forming a common electrode and a color filter layer on a firstsubstrate;

constructing a second substrate from an array substrate on which areformed a gate bus line layer, a gate insulating film layer, a drain busline layer, a protective film layer, and a pixel electrode layer;

forming fine slits in the pixel electrode layer in such a direction thata pixel is divided by the slits into at least two sub-regions;

forming on each of the two substrates a vertical alignment film forvertically aligning liquid crystal molecules;

forming a liquid crystal layer by filling an n-type liquid crystalcomposition having a negative dielectric anisotropy into a gap betweenthe two substrates, the liquid crystal composition containing anultraviolet curable resin having a liquid crystal backbone;

radiating ultraviolet light while applying to the liquid crystalmolecules a voltage not smaller than a threshold value of the liquidcrystal molecules, thereby defining the direction in which the liquidcrystal molecules tilt in the presence of an applied voltage; and

arranging two polarizers on top and bottom surfaces of the liquidcrystal display device in a crossed Nicol configuration with theabsorption axes thereof oriented at an angle of 45 degrees to thealignment directions of the liquid crystal molecules.

(Item 37)

A method of fabricating a liquid crystal display device as described initem 36, wherein the step of radiating the ultraviolet light to theliquid crystal composition injected between the two substrates isdivided in two or more steps and performed by using ultraviolet light ofdifferent intensities.

(Item 38)

A method of fabricating a liquid crystal display device as described initem 36, wherein the step of radiating the ultraviolet light to theliquid crystal composition injected between the two substrates isdivided in two steps consisting of the step of radiating the ultravioletlight while applying to the liquid crystal molecules a voltage notsmaller than the threshold value of the liquid crystal molecules and thestep of radiating the ultraviolet light without applying a voltage tothe liquid crystal molecules.

(Item 39)

A method of fabricating a liquid crystal display device as described initem 36, wherein the step of radiating the ultraviolet light to theliquid crystal composition injected between the two substrates isdivided in two steps and performed by applying respectively differentvoltages to the liquid crystal molecules.

(Item 40)

A method of fabricating a liquid crystal display device as described initem 36, wherein the step of radiating the ultraviolet light forpolymerizing the ultraviolet polymerizable component contained in theliquid crystal composition injected between the two substrates isdivided in two or more steps and performed by using a plurality ofultraviolet radiation units of different light intensities.

(Item 41)

A method of fabricating a liquid crystal display device as described initem 36, wherein the ultraviolet radiation to the liquid crystalcomposition injected between the two substrates is applied from thearray substrate side.

(Item 42)

A method of fabricating a liquid crystal display device as described initem 36, wherein the second substrate is constructed from an arraysubstrate on which the color filter layer is formed, the commonelectrode being formed on the first substrate, and the ultravioletradiation, onto the liquid crystal composition injected between the twosubstrates, is applied from the first substrate side.

(Item 43)

A liquid crystal display device fabricated by a method described in anyone of items 36 to 42.

The liquid crystal display device according to the sixth aspect of theinvention can be summarized as follows:

(Item 44)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein any portion where cellthickness varies by 10% or more due to design constraints is located ata liquid crystal domain boundary.

(Item 45)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a contact hole thatconnects between a source electrode and a pixel electrode is formed at aliquid crystal domain boundary.

(Item 46)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a contact hole thatconnects between a Cs intermediate electrode and a pixel electrode isformed at a liquid crystal domain boundary.

(Item 47)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, and liquid crystal alignment isdivided between two or more sub-regions, wherein more than one portionwhere cell thickness varies by 10% or more due to design constraintsdoes not exist.

(Item 48)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, and liquid crystal alignment isdivided between two or more sub-regions, wherein more than one contacthole is not formed in the same sub-region.

(Item 49)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a pixel electrode, asource electrode, and a Cs intermediate electrode are connected by asingle contact hole.

(Item 50)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein a metal electrode isadded along a liquid crystal domain boundary within a display pixel.

(Item 51)

A liquid crystal display device in which a liquid crystal layer issandwiched between a pair of substrates having electrodes, and a pretiltangle of liquid crystal molecules and a tilt direction thereof in thepresence of an applied voltage are controlled by using a polymer thatpolymerizes by heat or light radiation, wherein an electrode having thesame potential as a pixel electrode is not added in a slit portion ofthe pixel electrode within a display pixel.

(Item 52)

A liquid crystal display device as described in any one of items 44 to51, wherein the liquid crystal layer is sandwiched between a substratein which a color filter layer of red, blue, and green is formed on a TFTsubstrate, and a substrate on which a common electrode is formed.

The fabrication method for the liquid crystal display device accordingto the fifth aspect of the invention can be summarized as follows:

The fabrication method for the liquid crystal display device accordingto the seventh aspect of the invention can be summarized as follows:

(Item 53)

A method of fabricating a liquid crystal display device, comprising:forming a liquid crystal layer by filling a liquid crystal compositioncontaining a polymerizable monomer into a gap between two substrateseach having an electrode and an alignment film; and polymerizing themonomer by radiating ultraviolet light to the liquid crystal compositionwhile applying a prescribed liquid crystal driving voltage betweenopposing electrodes, and wherein: after polymerizing the monomer,additional ultraviolet radiation is applied to the liquid crystalcomposition without applying the liquid crystal driving voltage or whileapplying a voltage of a magnitude that does not substantially drive theliquid crystal.

(Item 54)

A method of fabricating a liquid crystal display device as described initem 53, wherein the additional ultraviolet radiation is applied usingultraviolet light whose wavelength is different from that of theultraviolet light used for the polymerization of the monomer before theapplication of the additional ultraviolet radiation.

(Item 55)

A method of fabricating a liquid crystal display device as described initem 53 or 54, wherein the ultraviolet light used in the additionalultraviolet radiation has a spectrum having a maximum energy peak at 310to 380 nm.

(Item 56)

A method of fabricating a liquid crystal display device as described initem 55, wherein the ultraviolet light used in the additionalultraviolet radiation has a spectrum having a maximum energy peak at 350to 380 nm.

(Item 57)

A method of fabricating a liquid crystal display device as described initem 55, wherein the ultraviolet light used in the additionalultraviolet radiation has a spectrum having a maximum energy peak at 310to 340 nm.

(Item 58)

A method of fabricating a liquid crystal display device as described inany one of items 53 to 57, wherein the additional ultraviolet radiationis applied for 10 minutes or longer.

(Item 59)

A method of fabricating a liquid crystal display device as described inany one of items 53 to 58, wherein substrate surfaces are treated forvertical alignment in accordance with a vertical alignment mode, andliquid crystals in a non-display area also are substantially verticallyaligned.

What we claim is:
 1. A liquid crystal display device comprising: a pairof substrates, defined as a first substrate and a second substrate; aliquid crystal layer sandwiched between the pair of substrates; a pixelelectrode and an additional electrode formed on the first substrate; anda contact hole that is configured and arranged to connect the pixelelectrode and the additional electrode, wherein the contact hole isformed at a liquid crystal domain boundary, and wherein said pixelelectrode includes a plurality of pixel electrode slits arranged in apattern to form a plurality of liquid crystal domains within each pixel.2. The liquid crystal display device according to claim 1, wherein thepixel includes four of said liquid crystal domains, which four domainsare formed by said pattern of said plurality of pixel electrode slits.3. The liquid crystal display device according to claim 1, wherein theadditional electrode is formed between the pixel electrode and the firstsubstrate.
 4. The liquid crystal display device according to claim 1,wherein the additional electrode is one of a source electrode or a Csintermediate electrode.
 5. The liquid crystal display device accordingto claim 1, further comprising a first vertical alignment film formed onthe first substrate and a second vertical alignment film formed on thesecond substrate.
 6. The liquid crystal display device according toclaim 5, further comprising a first polymer layer formed on the firstvertical alignment film and a second polymer layer formed on the secondvertical alignment film.
 7. The liquid crystal display device accordingto claim 6, wherein a tilt direction of liquid crystal molecules in thepresence of an applied voltage is controlled by the first and secondpolymer layers.
 8. The liquid crystal display device according to claim1, further comprising: a third electrode formed on the first substrate;and a second contact hole that is configured and arranged to connect thepixel electrode and the third electrode, wherein the second contact holeis formed at the liquid crystal domain boundary.
 9. The liquid crystaldisplay device according to claim 1, further comprising: a thirdelectrode formed on the first substrate; and a second contact hole thatis configured and arranged to connect the pixel electrode and the thirdelectrode, wherein the second contact hole is formed at a second liquidcrystal domain boundary, wherein said second liquid crystal domainboundary associated with said second contact hole differs from saidliquid crystal domain boundary associated with said contact hole. 10.The liquid crystal display device according to claim 8, wherein theadditional electrode is a source electrode and the third electrode is aCs intermediate electrode.
 11. The liquid crystal display deviceaccording to claim 9, wherein the additional electrode is a sourceelectrode and the third electrode is a Cs intermediate electrode.
 12. Aliquid crystal display device comprising: a pair of substrates, definedas a first substrate and a second substrate; a liquid crystal layersandwiched between the pair of substrates; a pixel electrode, a secondelectrode and a third electrode formed on the first substrate; a firstcontact hole that is configured and arranged to connect the pixelelectrode and the third electrode; and a second contact hole that isconfigured and arranged to connect the pixel electrode and the secondelectrode, wherein the first contact hole is formed within a firstliquid crystal domain and the second contact hole is formed within asecond liquid crystal domain, and wherein said pixel electrode includesa plurality of pixel electrode slits arranged in a pattern to form,within each pixel, the first and second liquid crystal domains.
 13. Theliquid crystal display device according to claim 12, wherein the secondelectrode is a source electrode and the third electrode is a Csintermediate electrode.
 14. The liquid crystal display device accordingto claim 12, wherein the pixel includes four of said liquid crystaldomains, which four domains are formed by said pattern of said pluralityof pixel electrode slits.
 15. The liquid crystal display deviceaccording to claim 12, wherein both the second electrode and the thirdelectrode are formed between the pixel electrode and the firstsubstrate.
 16. The liquid crystal display device according to claim 12,further comprising a first vertical alignment film formed on the firstsubstrate and a second vertical alignment film formed on the secondsubstrate.
 17. The liquid crystal display device according to claim 16,further comprising a first polymer layer formed on the first verticalalignment film and a second polymer layer formed on the second verticalalignment film.
 18. The liquid crystal display device according to claim17, wherein a tilt direction of liquid crystal molecules in the presenceof an applied voltage is controlled by the first and second polymerlayers.